NATIONAL INSTITUTE OF GENETICS(JAPAN)ANNUAL REPORT
No.2.

(1 95 1)----oo-~-PUBLISHED BY

THE NATIONAL INSTITUTE OF GENETICS(MISIMA, SIZUOKA-KEN, JAPAN)

1 952

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NATIONAL INSTITUTE OF GENETICS (JAPAN)
ANNUAL REPORT
No.2 (1951)

Contents
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General statement. . . . .
Abstract of diary in 1951 .
Staff . . . . . . . . . . .
Council.
Research program for 1951 .
Researches carried out in 1951.
A. Human genetics.
1. Japanese pedigrees of typical brachydactyly.
2. Genetic and aetiological studies on microcephalic idiots.
B. Cat genetics. . . . . . . . . . . . . . . . . . . .
C. Silkworm genetics.
1. Genetical interrelationship between modifiers of multilunar,
multistars and knobbed in the silkworm. . . . . . . . . .
2. Modifiers of the genes for multilunar, multistars and knobbed
characters. . . . '. . . . . . . . . . . . . . . . . . . . .
3. Unstable genes or polygenes?
4. Appearance of a recessive retarded strain from a dominantretarded strain in the silkworm . . . . . . . . . . . . . .
5. Changes of the long-day effect to a neutral one in the photoperiodism of a wild silkworm, Antheraea pernyz" . . . "6. Studies on the so·called multiallelic E-series in the silkworm .
A. Studies on the new multi-star-marking gene EM.
B.

Larvae of the genotype

EHEKP

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7. "Lethal yellow" gene in Bombyx and its relation to "Lemon". 17
8. Sterility in the silkworm due to an abnormality in the bursa
copulatrix. . . . . . . . . . . . . . . . . . . . . . . . . 18
9. On the relation of penetrance of a gene·(or a gene'set) causing
malformation to enviromental conditions. . . . . . . . . . 19
10. The effect of centrifugal force upon the development of silkworm and eri-silkworm eggs.

A. Induction of malformations. . . . . . . . .
B. Embryological observations. . . . . . . . .
D. Genetics of polymorphism in some invertebrates.
1. The lady·beetle Harmonia. . . . .
2. The lycaenid butterfly Neozephyrus
3. The pierid butterfly Colias.
4. The land-snail Bradybaena. . . . .
E. Genetics of some cereals.
1. Radiation genetics in einkorn wheat.
2.' Nullisomic dwarfs in vulgare wheat and gigas-plants in theiroffspring . . . . . . . . . . . . . . . . . . . . . . . .
3. Studies on Agropyrum, a genus related to Triticum . . . .
4. Morphologically different twins found in the progeny of a
hybrid wheat . : . . : . . . . . . . . . . . . . . . . .
F. Genetics and cytology of lVicotiana.
1. Cytogenetic studies in the genus Nicotiana II.
A. On the meiotiC chromosomes of ten wild and one cultivatedspecies of the genus Nicotiana~ . . . . . . . . . . .
B. Cross between N. glutinosa and N. sylvestris. . . .
C. Hybrid between N. glauca and N. plumbaginifolia.
2. Cytogenetic studies on the genus Nicotiana III. . . .
3. Mutations in tobacco induced by X-rays. . . . . . .
4. Studies on the relative weight of mid-rib in Nicotiana tabacumleaves. . . . . . . . . . . . . . . . . . . . . . . . . . .
G. Genetics of Capsicum.
1. Genetic studies on some fruit characters in Capsicum annuum.
2. Decline of fruit productivity by artificial selfing in Capsicum
annuum
,H. Genetics of eggplant.
1. Studies on developmental processes of fruits in eggplants. .
2. Regression analysis of fruit-shape and -size genes with the aidof F 1 hybrids in eggplants. . . . . . . . . • .
3. Studies on combining ability in eggplant varieties . . . . .
I. Cytology and genetics of some flowering plants.
1. . Karyological studies on Narcissus I. . . . . . . .
2. Cytogenetic studies on the sex in Cannabis sativa L. I..
3. Irregular mitosis in some clones of the genus Cole hicum.
4. Progeny of Lycoris radiata . . . . . . . . . .
5. Genetics of flower characters in Zinnia elegans . . . . .
6. Sterility in Phaseolus multijlorus. . . . . . . . . . . . .
7. Paper chromotographic studies of flower color variation.
J. Improvement of some useful plants.
1. Improvement of sugar beets by means of induced triploidy..

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Genetics and breeding of Citrus.
A. Parthenocarpy and seed reproduction .
. . . . . . ..
B. Polyembryony
3. Induced polyploidy in some cultivated plants and its utilization.
A. Polyploid watermelons· (Citrullus vulgaris).
B. Grafting stocks for triploid watermelons
C. Tetraploid melon (Cucumis Melo). . . .
D. Tetraploid race of Medicago dentz"culata
K. Studies on some lower organisms.
1. Effect of X-ray irradiation on Streptomyces griseus.
2. On a heterokaryon in Aspergillus candidus . . . .
3. Studies on Neurospora crassa.
A. Rate of production of fruit-body in different culture filtrates.
B. Growth promotion of culture medium filtrates of two mating
types. . . . . . . . . . . . . . . . . . . . . . . . . .
4. Studies on the virus infecting the silkworm.
A. On a method of propagation of the virus infecting thesilkworm. . . . . . . . . . . . . • . . . . . . . . .•B. On the multiplication and growth of virus in living cells.
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L.

Theoretical genetics.
1. Experimental demonstration of the theory of variance increase
due to competition in plant populations. . . . . . . . . .
2. Competition studies with six varieties of rice. . • . . . . . •3. Theoretical studies on selection in the breeding of autogamousplants. . . . . . . . . . . . . . . . . . . . . . . . . . .
4. Fluctuations of adaptive values and the frequency distributionof heterotic genes in natural populations.
A. Long term distribution determined by random fluctuation.
B. Process of the change of gene frequencies due to the cyclic
and random fluctuations of selective values • . • • . ••5. Process of irregular change of gene frequencies due to therandom fluctuation of selection intensities. . . • • . • .•6. On "effective size of populations". . . . . . . . . . . • . .
7. On the process of decay of variability due to random extinctionof alleles. . . . . . . . . . . . . . . . . . . . . . . . •8. Process of recombination of chromosome segments in a random
breeding population. . . . . . . . . . . . . . . . . . . .
9. Method of mating-operators and its application to the studyof partially self-fertilizing populations. • . . . .
10. Statistical theory on the pre- and post-reduction of chromosomes. . . . . . . . . . . . . . . . . . .
Papers and books written by the members of the staff •

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Addendum
1. The Misima Branch of Hatano Tobacco Experiment Station of
the Japan Monopoly Corporation . . . . . . . . . • . . . . 70
2. The Association for the Propagation of the Knowledge ofGenetics (Idengaku Hukyu-kai). . . . . . . . . .
70
3. The Whole-Japan Association of Poultry Genetics. . . . . . . 70

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GENERAL STATEMENT,

In 1951 the equipment of the Institute improved, and all its
research activities made good progress. The main building which
had been rented from the Fuji Industrial Company was purchased
for the exclusive use of the Institute. Two new small buildings,
one for breeding rats and mice and the other for silkworm culture,
were completed and are in use. The land which had belonged to
the Ministry of Education was legally transferred to the Institute.
Also a piece of land 4,418 tubo (3.61 acres) in size was rented in
the neighborhood as a nursery for rare varieties of cultivatedtrees and shrubs, as well as for the site of staff re3idences.
The library has been expanded by the addition of several backseries and numerous current numbers of periodicals and many new
books. Dr. R. GOLDSCHMIDT has continued to send reprints, journals
and books newly acquired by him to bring the library which wasformerly his own up to date. These new publications are very
valuable, especially as our subscriptions to current journals areregretably limited.
Prof. S. MAKINO of Hokkaido University was appointed part-timemember of the Institute. He is currently on leave for one year
to study cytology in the United States. Research assistants M.
OGAKI and S. KAJI resigned and were replaced by S. TSUDA andK. TUTIKAWA respectively. The number of regular members of
the Institute has been raised from 33 to 38, by the addition of
5 field laborers.
S. MATSUMURA was awarded the Genetics Prize by the Genetic
Society of Japan for his investigations on pentaploid wheat. T.
KOMAl was elected corresponding member of the American
Society of Human Genetics.
A number of research grants were received during the year
by our staff. These have been of great aid to our research programs.
The Ministry of Education granted from the Scientific Research
Fund the following sums to our members to aid their respective
researches :K. OGUMA and coworkers (including T. KOMAl, K. TUTIKAWA):1

Breeding and reservation of strains of rats and mice suited for
medical research purposes- ¥730,000;
T. KOMAI and coworkers (including K. SAKAI and M. KIMURA):
Researches in population genetics- ¥500,000,(Individual research items: T. KOMAI: Researches in population
genetics with insects and a land-snail as materials, K. SAKAI:
Competition between plants of different genotypes in a population, M. KIMURA: Theoretical researches on population genetics);
Y. TANAKA and coworkers (including M. TSUJITA): Fundamental
and applied genetics of the silkworm- ¥350,000,(Individual research items: T. TANAKA: Phenogenetics of thesilkworm, M. TSUJITA: Embryological and physiological geneticsof the silkworm);
S. MATSUMURA: Radiation genetics of wheat and barley¥40,000;

S. MATSUMURA: Breeding of wheat strains resistant to rust bymeans of the D-genome substitution- ¥ 40,000.
The following researches were supported by the grants fromthe Scientific Experiment Fund of the Ministry of Education:S. MATSUMURA and coworkers: Breeding of triploid sugar-beetstrains- ¥100,000;
M. TSUJITA and coworkers (including B. SAKAGUCHI): Studies
on lethality and failure of fertilization in the silkworm- ¥50,OOO.
The Ministry of Education also gave the following extra-budgetary
sums to the Institute:Expense for construction of constant temperature room used forthe preservation of silkworm eggs and Drosophila strains¥1,100,000;

Expense for purchasing an ultra-thin sectioning microtome~¥216,000.

The Ministry of Agriculture and Forestry granted from its fundfor promoting investigations on techniques in agriculture, forestry
and fishery to
K. SAKAI: Investigation on the efficacy of the bulk-breeding
method- ¥100,000.
Y. TAKENAKA gave from November 5 to 12 a series of lectures
on genetics in Kanazawa University.
Among the large number of visitors was Prof. H. J. MULLER
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yof Indiana University. Prof. MULLER spent a week from April 8
to 15 in Japan on his trip back from India to the States. Afteran extremely busy two-and-half day program in Tokyo, being
received in audience by the Emperor, attending a welcome party
sponsored by the Japan Academy, delivering a public lecture toa large audience and visiting Tokyo University and the Sericulture
Experiment
Institution, .
he came to
Mjsjma on
the 11th atabout 10o'clock jn
the mornjng.
He
he a r d r eports of four
genetjcists
fro m outsjde the
Instjtute on
the recent
outcomes of
their studiSCHULL, SINOTO, KIHARA,
es. He next
MULLER, OGUMA, KOMAI, TANAKA.
gave a lecture on recent advances in genetics to an audjence which
consisted of the members of the Institute and many other biologists
who had come to hear the well-known geneticist from all parts ofJapan. He then went around the Institute and inspected the workof the members. In the evening he left Misima, and went to Atami,
where he dined with the five senior members of the Institute (Fig.).
He took a night train from Atami to Hiroshima with Drs. W. J.
SCHULL of A.B.C.C., KIHARA and KOMAI. After inspecting the workin progress at the A.B.C.C. and giving a lecture at Hiroshima
University, he stopped over at Kyoto on his way back, and gave
another lecture in Kyoto University. On the whole, Dr. MULLER'S
visit was highly beneficial not only to the Instjtute, but also togenetics and biology in Japan at large.
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ABSTRACT OF DIARY IN 1951
January 15. A 4,418 tubo (3.61 acres) plot of land at Sironouti,
Yata, in Misima was rented to be used as a nursery of usefulplants and site of residences of the staff.
January 27. Third meeting of Misima Geneticists' Club.
February 24. Fourth meeting of Misima Geneticists' Club.
March 3. Board meeting of Association for the Propagation of
the Knowledge of Genetics.
March 4. Committee meeting of the Genetic Society of Japan,
Joint meeting of the National Committee of Genetic
Researches and the National Committee of Researches in
Plant and Animal Breeding of the Japan Science Council.
March 20. The land 24,524 tubo (20.01 acres) in extent has
legally become the property of the Institute.
March 21. A part of the main building, 764.32 tubo in floor area,
was purchased from the Fuji Industrial Company.
April 1. The number of regular members of the Institute wasraised from 33 to 38. The office of the Genetic Society ofJapan was moved from Tokyo University to the Institute.
April 11. Dr. H. J. MULLER visited the Institute and gave alecture (see the foregoing report). The joint meeting of the
National Committee of Genetic R9searches and the National
Committee of Researches in Plant and Animal Breeding ofJapan Science Council. Fifth meeting of Misima Geneticists'
Club. Meeting of Sizuoka Plant and Animal Breeders' Club.
May 11. Sixth meeting of Misima Geneticists' Club.
May 14. Fifth meeting of the Board of Councillors.
June 15. Seventh meeting of Misima Geneticists' Club.
July 31. Miss Carlyn HALDE'S lecture on dermal diseases causedby parasitic molds.
November 18. Eighth meeting of Misima Geneticists' Club.
December 19. Meeting for interim reports on the fundamental
studies for the improvement of tobacco plants.
December 22. The remaining part of the main building, 401.34
tubo floor area, was purchased. Ninth meeting of Misima
Geneticists' Club.

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STAFF

Department and Laboratory Heads
Kan OGUMA, D. Agr., Director, and Head of the Second Department
Yoshimaro TANAKA, D. Agr., D. Sc., Head of the First Department
Taku KOMAl, D. Sc., Head of the Third Department

Part-time Staff
Hitoshi KIHARA, D. Sc., Professor of Kyoto University
Yosito SINOT6, D. Sc., Professor of Tokyo University
Sajiro MAKINO, D. Sc., Professor of Hokkaido University

Laboratory Heads
Yo TAKENAKA, D. Sc.
Kan-Ichi SAKAI, D. Agr.
Seiji MATSUMURA, D. Agr.
Mitsuo TSUJITA, D. Agr.
Kazuo FURUSATO

Research Associate
Yoshinari KUWADA, D. Sc.

Research Assistants
Mota KIMURA
Kanji GOTOR
Taro ITO
Bungo SAKAGUCHI
Toru END6
Akira MIYAZAWA
Kiyosi TUTIKAWA
Seizo TSUDA
Temporary Assistants 10

Department of Administration•

Morihei TSUKAMOTO, Head of Department
Sumiyoshi Sumo, Head of General Business Section
Masao MIYAZAWA, Head of Finance Section
Naomi MATSUBARA
Hiroko NAKANO
JunzQ KADOWAKI
Typist, Telephone operator, Chauffeurs, Field laborers, Janitors,

ete.-14.
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Misima Branch of Hatano Tobacco Experiment Station
Masao TANAKA, Head
Flora A. LILIENFELD, Ph. D.
Seiji IMAI
Assistants-3.
Whole"Japan Association of Poultry Genetics
Kan OGUMA, President
Yoshimaro TANAKA, Director of Researches
Take NAKAMURA, Managing Director
Association for Propagation of the Knowledge of Genetics
Kan OGUMA, President
Yo TAKENAKA, Managing Director
Seiji MATSUMURA, Managing Director
COUNCIL

YO K. OKADA, Professor of Tokyo University, Chairman
Seishi KAYA, Professor of Tokyo University, Vice-chairman
Konosuke AKIYAMA, President of Japan Monopoly Corporation
Eikichi HIRATSUKA, Director of Agricultural Technique ResearchInstitute
Seizo KATSUNUMA, President of Nagoya University
Makita KOGURE, Professor of the Tokyo College of Agriculture
and Technology
Yoshio KOYA, Director of the Institute of Public Health
Kiyoshi MASUI, Emeritus Professor of Tokyo University, Professorof Nagoya University
Bungo MIYAZAWA, President of Woman's College of Anjo University
Toshitaro MORINAGA, Head of the Department of Physiology andGenetics of Agricultural Technique Institute
Waro NAKAHARA, Director of Cancer Research Institute
Masanori NAKAIZUMI, Professor of Tokyo University
Yusuke SUMIKI, Professor of Tokyo University
Yfishi UCHIMURA, Professor of Tokyo University
Yasuke YAMAGUTI, Professor of Ibaraki University

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RESEARCH PROGRAM FOR 1951"

Tanaka LalJoratory
Unstable genes-TANAKA
Selection and stability of genes-TANAKA
Genetic study of the dominant retarded silkworm-TANAKA
Genetic analysis of the recessive retarded silkworm-TANAKA
Photoperiodic effect on the diapanse of a wild silkworm Antheraea
pernyi-TANAKA
Matsumura Laboratory
Radio-genetic studies on wheat-MATSUMURA and FUJII'Agropyrum as a close relative of Triticum-MATsuMURA
NuIIisomics found among the progeny of pentaploid hybrid wheat-MATSUMURA
Breeding of triploid sugar beet-MATsUMURA, MOCHIZUKI (Kyoto
Univ.), et aI.
Mutation in Nicotiana by X-ray irradiation-KIHARA, MATSUMURA
and FUJII
Breeding of strain of· wheat resistant to rust-MATSUMURA andHIRATSUKA (Tokyo Univ. of Education)
Triticale-END6
Furusato Laboratory
Breeding of Citrus varieties-FuRuSATO and MIYAZAWA
Production and breeding of polyploid plants-FuRUSATO
Biochemical genetics of flower colors-END6 and MIYAZAWA
Oguma Laboratory
Origin of sex-chromosomeS-OGUMA
Phylogeny of animals and plants based on karyotype analysisOGUMA, SINOT6 and TAKENAKA. Genetics of right- and left-handedness· in plant organs-KIMuRA
Theoretical studies of population genetics-KIMURA
Origin of the plants of the genus Lycoris and their distribution-KIHARA and LILIENFELD
Cytogenetics of rat and mOUSe-OGUMA and TUTIKAWA
Takenaka LalJoratory
Collection and preservation of varieties of useful plants-TAKENAKA
Origin of sex-differentiation in higher plants-TAKENAKA
Cytogenetics of some fungi-SINoT6 and IT6
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Komai Laboratory
Genetics of microcephaly in man-KOMAI, KIsmMoTo (Nagoya
Univ.) and OZAKI (Inst. Public Health)Japanese pedigrees of typical brachydactyly-KoMAI
Genetics of coat colors in cats, and the problem of origin of
tortoiseshell male-KoMAI
Population genetics of the lady-beetle Harmonia-KOMAI
Genetics of the butterflies Colias and Neozephyrus-KoMAI
Population genetics of the land-snail Bradybaena-KoMAI
Sakai Laboratoay
Genetics of fruit-crops-SAKAI and GOTOH
Competition between plant individuals having different genetic~onstitutions-SAKAI and GOTOH
Theoretical and experimental studies on selection in plant breeding-8AKAI
Genetic study of competitive capacity of plant individuals-SA.KAl
Genetic studies on flowering shrubs-GoToH
Tsujita Laboratory
Virus infecting silk-producing insects-TsUJITA and SAKAGUCm
Lethal eggs and sterility in silk-worm-TsuJITA and SAKAGUCHI
Manifestation of gene effects-TsUJITA and SAKAGUCm
Developmental genetics of silk-worm-TsuJITA and SAKAGUCHIMinute structures of chromosome-TsuJITA and SAKAGUCHI
Cytogenetics of silk-worm,especially polyploids-TsUJITA
Research Students and their Research Items:
Kozo NAKAMURA: Polyploidy in plants
Yasuo SUZUKI: Breeding of polyploid plants
Seizo TSUDA: tenetics of useful molds
Kyozo WATANABE: Hybridization between local races of newts
Toru IWATA: Relation between chromosome number and specia·tion in plants

8"

RESEARCHES CARRIED OUT IN 1951

A.

HUMAN GENETICS(Report by Taku KOMAI)

1. Japanese Pedigrees of Typical Brachydactyly

Three kindreds of typical brachydactyly have been discovered recently
in Yokosuka, at a village near Matumoto (Nagano Pref.) and in Asiya(Hyogo Pref.). These include respectively 10, 18 and 6 patients besides afew doubtful cases. The abnormality consists of marked degeneration of
the middle phalanges of all fingers and toes. This has been confirmed
by X-ray photos of the hands and feet of some patients. Each kindredshows peculiarity in the details of the abnormality. The patients in the
Matumoto kindred show abnormality almost identical to that in the patientsin DRINKWATER'S English pedigree and in ILTIS' American pedigree. The
inheritance is monogenic, the abnormal character being dominant withperfect penetrance.

2. Genetic and Aetiological Studies on Microcephalic Idiots
Since last year, materials have been gathered for study of this severecongenital defect. So far nearly 60 cases have been obtained. Anthropometric and psychological tests have been conducted and pedigrees followed for nearly all of them. The patients are idiots of the extreme degree,
the mental age being 2 at best. This abnormality is apparently due toa recessive gene. Complications, however, seem to exist. There are somecases which seem to be caused by simple developmental haphazard, without any relation to heredity. The present study will be nearly completed by the end of this year. It is expected that some data of generalinterest will be disclosed.

"
B.

CAT GENETICS(Report by Taku KOMAI)

Inheritance of Common Color Types and the Origin of
Tortoiseshell Male
Census of cat populations have been conducted in Misima and Gotemba,
as well as in several towns in Hokkaido, and the results have been analyzed with respeCt to the frequency and the location of the genes for9the common colors. Undisputable evidence has been obtained by thisprocedure of the sex-linkage of the gene for orange color and of thepresence of the genes for tabby and black in an autosome. AmongJapanese cats the frequency of the gene for orange is much higher thanamong the cats in London, the former being as high as 25-40 per centas compared with the 10.7 per cent given as SEARLE'S figure for the latter.
Fourteen specimens of tortoiseshell males have been examined, besides
data on their mothers and litter mates. It has become clear that a tortoiseshell male can be produced by either a tortoiseshell mother, or by
an orange or a black mother. Sections of testes of two of these specimens have been examined. They show characteristics of testes of perfect sterility, but nothing suggesti~g an intersexual gonad. These findings do not accord with the working hypothesis formally proposed by
the writer. It is more plausible that the cause of the production of thiskind of abnormal individual lies in the germ cell of the father, insteadof that of the mother. If crossing-over takes place between the X andY chromosomes in the spermatocyte of the father, the gene for theorange color 0 or its allele 0+ may be transferred from X to Y. Reciprocally, the gene-complex for fertility of the male may be transferred fromY to X. The son which receives such a crossover Y will become tortoiseshell and sterile. This hypothesis postulates a gene-complex for fertility in Y whose presence has never been demonstrated in any mammalian Y chromosome. This postulate has been made from the analogyof the construction of the Y chromosome in Drosophila, and it does notseem to be very improbable, if applied to the case in a mammalian cell.

C.

SILKWORM GENETICS

1. Genetical Interrelationship between Modifiers of Multilunar,

Multistars and Knobbed in the Silkworm(Report by Yoshimaro TANAKA)

When two characteristics of skin, either multilunar (L) and multistars(ms), or multilunar and knobbed (K), or multistars and knobbed, coexist
in the same individual, both characters exactly coincide in arrangementof composite spots and protuberances. For example, if L spots develop
in each of the 4th to the 8th larval segments, the coexisting knobbed
is also found in exactly the same segments. In any segment where an
L spot is unpaired, the knob, if K gene is present, is invariably onesided.
This fact seems to indicate that these characters have cOII1mon modifiers which determine the arrangement of spots and knobs. The present

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study, however, has disclosed that there is no ground ror this supposition, as shown by the following findings:a) There are characteristic arrangement patterns in the offspring foreach of the three characters in question.
b) These characteristic patterns reappear in the offspring, whenever
the major genes, L, ms, and K, are segregated in F 2 and later generations.
It is evident, therefore, that the coincidence in arrangement of thesespots and knobs when they occur in the same individual is not of agenetic nature, but is due to a similarity in the developmental mechanism
of. these characters which are all related to the skin, especially to thedermal pigment.

2. Modifiers of the Genes for Multilunar, Multistars andKnobbed Characters(Report by Yoshimaro TANAKA)

Studies on the numbers and kinds of modifiers of these three charactershave not yet been completed. The following list is therefore a tentative
one.
a) Modifiers controlling the arrangement types of multilunar.

L lO Produces L spots in segments 4-10
14 Produces L spots in segments 4-9
Ls Produces L spots in segments 4-8 (the standard type)
L 4S Suppresses L spots in segment 4
L 6S Suppresses L spots in segmenf 6
L 7B Suppresses L spots in segments 6 and 7b) Modifiers controlling the arrangement types of multistars
JnS4-10 Produces star spots in segments 4 and 6-10
mS6-10
Produces star spots in segments 6-10
JnS6-9Produces star spots in segments 6-9
JnSS-lO Produces star spots in segments 8-10
JnSS,9Produces star spots in segments 8 and 9
JnSs
Produces star spots in segment 8 (apparently + p type)
JnSo
Produces no star spotc) Modifiers controlling the arrangement types of knobbed
Ks
Produces knobs in segments 2,3,5,8 (the standard type)
K9
Produces knobs in segments 2,3,5,8,9
Ka.7 Produces knobs in segments 2,3 and 5-8
K lO Pr oduces knobs in segment 10 (irrespectively of other segments)11

!J. Unstabie Genes or Poiygenes?
(Report by Yoshimaro TANAKA)
MATHER'S theory of polygenes had been devised primarily to explain
the effect of selection. The author's hypothesis of unstable genes also
stands on the basis of effective selection. It seems therefore desirable toexamine whether the polygene theory could be applied to the case insilkworm. I find some difficulties in explaining the results thus far obtained on the basis of the polygene hypothesis in connection with thefollowing points:a) According to the polygene theory, the variation in F 1 of a crossbetween two inbred strains is nearly the same in extent as in the parents ;in F 2 it suddenly increases and attains a maximum value; then it gradually decreases in later generations.
This is not the case with the unstable genes governing the' arrangement types of L, ms and K characters. To give an instance, the crossbetween two strains having different L arrangement types, both intensely
inbred, has often shown variability which is highest in F 10 and decreases
gradually in F 2 and later generations. The 0 type of ms marking is another example. Although it is an established strain, it sometimes segregates only in a negligible percentage in F 2 of the cross with the 8-10
type, and often it does not appear at all. In other crosses the 0 typeoccurs as early as F 1, and in still others appears first in F 3.
b) In contradiction to the expectation of the polygene theory, no arrangement type characteristic to L, ms and K becomes fixed, nor doesit breed true even after a considerable number of generations of selection
by inbreeding. The strains throw. more or less different types in eachgeneration, from which it is possible to breed a new type by selection.

•

4. Appearance of a Recessive Retarded Strain froma Dominant Retarded Strain in the Silkworm(Report by Yoshimaro TANAKA)

In a strain which was produced by X-ray irradiation and presumably
involves a deficiency and an inversion in chromosome II, the two characters p (plain marking) and Y (yellow blood) are inherited together as
if they were completely linked. The heterozygotes are characterized byretarded development, small body size and small cocoon. The homozygotes mostly pass through the embryonal stage, but perish as larvae. or
pupae. The lethal action of this aberration therefore is apparently rather
weak. This fact suggests tha! the deficiency in this strain is coQiparatively small. I mentioned in former papers (1934, 1935) that no eros-

12

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•

sing-over occurs between p and Y in this strain. Later, however, I ascertained the occurrence of a small amount, about 1. 7%, of crossing-overbetween them. I shall tentatively designlte this dominant character for
retarded development by the symbol Rt.
In the second season of 1951, 3 cultures from the cross +/+ x Rt/+
were reared. One of them segregated + and Rt in a 1: 1 ratio, while
two produced two to three times as many + as Rt. A differential mortality was out of the question, because there was no marked difference inthe total numbers between hatched and grown larvae. It can be inferred: from the results in later generations that the dominant character for
retarded development changed to a similar but recessive one in a partof the germinal cells of the male parent.
In the next generation of normals from the culture in which normals
and retarded had segregated in a 1: 3 ratio, both types were produced
almost exactly in a 3 : 1 ratio. These normals were again mated among
themselves, and 3 cultures were reared. One lot gave normals only,
while the other two segregated normals and recessive retarded (designat.
ed by the symbol rd) in a 3 : 1 ratio.
What was the cause of the production of this recessive retardation
strain from the dominant retarded strain? Two considerations seem
possible.
a) A new recessive mutation occurred independently from the original
dominant character for retarded.
b) The chromosome aberration which had caused the dominant retardation changed in length or position through some segmental interchange,
and became a recessive character as in the case of the position effect of.. hairy" in Drosophila.
For the moment I cannot decide which is the correct explanation, but
I am inclined to adopt the second view, because there is a very close
similarity between the two retarded types, except for the reversed dominance relations. If this is established, the 'present case seems to be the~t example of position effect found in the domestic silkworm.

5. Changes of the Long-Day Effect to a Neutral One in the
PhotajJeriodism of a Wild Silkworm, Antheraea pernyi•(Report by Yoshimaro TANAKA)

The author (TANAKA, 1950) has proved that photoperiodism plays themost important role in determining the hibernating character of theChinese tussar silkworm, Antheraea pernyi GUER. When the larva is
exposed throughout its life to the short-day treatment, below 14 hours
per day, it becomes a hibernating pupa without exception. If it is exposed to ~ long-day treatment, over 15 hours per day, it invariably gives13

a non-hibernating pupa. The intermediate day'length, between 14 'and IShours per day exerts no positive effect; it shows a neutral b~havior as
to 'photoperiodism, and both hibernating and non-hibernating pupae areproduced. Constant light and constant dark do not, contrary to expec'"
tation, behave as extreme cases of long-day and short-day respectively;
their effects are similar and neutral.
In order to find how the long-day effect changes into the neutral one
under the constant exposure to light, the larvae were treated with ashort-day exposure (8 hrs) through I to IV instars, and only V instar'
was exposed to different light conditions. The results are as follows:
Lot No.
23-24
25-26
27-28
29-30
31-32

...

Day-length in V instar
Hibernating pupae, on the average
16 hrs per day
41.99618
52.3 ..
20..
83.8 ..
22
88.7 ..
24.. (constant light)
95.4 ..

The increase of the p~rcentage of hibernation in the classes from 16
hrs upwards to 24 hrs shows a decrease of the long-day effect or nonhibernation-inducing effect exerted upon the larvae in the last instar counteracting the short-day or hibernation-inducing effect imposed on themin I to IV instars. Thus we know that the long-day effect changes somewhat gradually to a neutral effect, although there is a remarkable gap
between 18 and 20 hours.
6.

Studies on the So-called Multi-allelic E-series
in the Silkworm(Report by Mitsuo TSUJITA)

A. Studies on the newmulti-star-marking gene EJfS
EMs'is a new gene belonging to the multiple-allelic E -series of the silkworm. EM. has originated apparently by mutation of EMS, though it
could be due to some change in chromosomal structure. TSUJITA andSAKAGUCHI are now studying the action ·of these genes in relation to theother alleles of the same series, such as Ell, EA'p, EIJ, ENl, EO", EN,E, from the embryological and genetical points of view. A general summary of the experimental results follows:1) Both EJ£8 and EM. have a markedly lethal action.' Embryos homozygous for E"!fS have supernumerary abdominal legs on the 10th and11th segments, and die in the later embryonal stages or immediately after
hatching. The embryos homozygou::l for EM. also die in later embryonal
stages or immediately after hatching; they have thoracic legs and thoracic setae on all segments, and are incapable of blastokinesis.
14

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2) Embryos of the heterozygotes EJf8/EIJ, EMs/EN, EMs/EGa and thoseof heterozygotes EMe/ED, EMe/EN, EMe/EGa die in the pigmentation
period. Supernumerary legs, or fusion of segments, or deformity of someinternal organs, may be observed in the lethal embryos.
3) It may be .noted that the percentage of lethal embryos is different
in reciprocal crosses between normal and EMS or EMe. When the motheris of the former type, the percentage of lethal embryos becomes much,
hjgher than in the reciprocal cross. The cause of this difference, however, remains to be clarified.
4) Very few individuals with a combination of the characters peculiar
to each type have been obtained by mating a normal female with a maleheterozygous for EMS or EMe in combination with other genes of thesame series. However, whether this is due to genetic recombination cannot be ascertained until the suceeding generation are examined.
5) In short, it appears that EMS and EMe are genes participating'in the formation of the larval structure in the early developmental
stages, and that they have a pleiotropic effect like other genes of the
E-series.
Ell,EKp
B. Larvae of the genlJiyPe---

+ +

•

l'

Fifteen genes E, EKp, EGa, EGr, EBt, ED, Ell" ENe, EN1', EDs, EMS,
EMe, ENS, EN, EA are located at the end of chromosome VI. It has beenshown that they form a multi-allelic series, although some workers haveexpressed their scepticism of this interpretation. Most of the genes produce extra-legs or extra-semilunar patterns or both on two or threeabdominal segments of the larva.
In a previous investigation, TSUJITA and SA~AGUCHI (1951) obtained individuals trisomic with respect to chromosome II. During 1951, experiments
were carried out to obtain individuals trisomic with respect to chromosome VI. This aim has not been attained, but some other interesting
facts, as described in the following paragraphs, were found. Males
heterozygous for the genes Ell, and EKP from the allelic series mentioned
above were dusted with :ij. H. C. powder, or treated with radiation ofhigh frequency waves. These treated males were mated with normal
females. As controls heterozygous males which had not been treatedeither with B. H. C. or radiation were mated with normal females.
Among the progeny of the former cross a small number of individuals
with combined Ell, and EKp types were found. Some such exceptional
larvae, however, were also obtained from the control lot., Therefore, it
seems that this apparent change in genetic constitution can occur without any relation to B.H.C. dusting or radiation.
Breeding tests of the individuals with the combined characters havedisclosed that they are due to the recombination of Ell, and EKp i.e.
15

EJiEEp++

These larvae have a phenotype which is more than the com-.

bination of the characters peculiar to EH and ENP, representing a new
type characterized by the presence of extra abdominal legs on the firstand second abdominal segments as well as of extra-semilunar patterns on
the first abdominal segment. They are thus easily distinguished fromEH+

the +ERP larvae.
EHENp

From the cross wild (+) x - - - a few EH and ENP larvae always++

segregate, obviously by recombination.
EHERP

Embryos of the genotype EHERP , have extra-legs which develop al·
most to the same size as the normal abdominal legs. Under a definite
environmental condition these embryos die immediately before the pigmentation period.

The phenotypes of

EHERP
EH +

and

EHEJCP+ EKp show a dis-tinction in that the extra-leg development is more pronounced in the
EHEJCP

former combination than in the latter. The phenotype of the++larvae can hardly. be distinguished from that of EEl. E also shows avery similar phenotype.
The gene EH has a slight lethal effect in the heterozygous state, while
the effect is somewhat stronger in the homozygote. The' gene ElCP has
little lethal action both in heterozygote and homozygote. The lethal
action of the genotype
E;P , orE~D++

is stronger than that of types~~.,~;t. There is little difference in the intensity of lethal
EHERP

EH

action between the 7t HEKP and the EH individuals.
.

lethal effect, the genotype

In the degree of

EH++EKP is almost the same as the genotype

EHERP
+EKP'

From the facts presented above*, it seems that the genes belonging to
the E-series behave a~ either allelic or tightly linked genes, and it is likely that the E "locus" is not a point but has a stretch of some extent.
Perhaps it consists of several genes with similar effects arranged in closesequence at the end of chromosome VI. This kind of gene group has
been called by various names (comp. KOMAI 1950); MULLER (1948) has calledit "semi-allelic genes".

The fact that the phenotype of

EXENP

+ +

is

* According to ITlKAWA (1951), some E.dENc/+ individuals due to recombinationbetween E.4. and ENe were obtained.
16

dearly different from the phenotype of~;~pshould be regarded' a~another good example of position effect which was demonstrated first in
Bar in Drosophila melanogaster.

•

7. "Lethal Yellow" Gene in Bombyx and its

Relation to "Lemon"(Report by Mitsuo TSUJITA)'.

•

The lethal yellow gene in the ,silkworm is recessive. The larvae,homozygous for this gene show a distinct yellow body color directly after
the first moulting and die within a few days because of their inability tofeed. The yellow color is due to the pigment "xanthopterine-B", contained mostly in the pigment granules of the hypodermal cells.
In order to make clear the relation between this lethal yellow and" lemon" which has a similar phenotypic effect, 9 batches of F 1 hybrids
between the homozygous lemon (tern/lern) and the heterozygous lethal
yellow (+ily) were examined. All larvae hatched from 3 of these batches
were normal, while normals and lemons were found in the ratio 1: 1
among the larvae hatched from the other 6 batches. No lethal larvae
were obtained from sib-matings of normal individuals produced in theformer as well as in the latter batches, but among the lemon larvae in
one of the latter batches about 25% were dead in the egg. Although it
might appear strange that we could not find any lethal yellow larvae immediately after the 1st moulting, the reason is easy to see. The full.grown embryo, which is of a yellowish brown color, cannot chew up
the chorion to hatch out, b~c:lu3e of the incomplete differentiation andinsufficient hardening of the mandibles. If such an embryo. is released
by cutting the chorion, it emerges as an apparently normal larva andmoves about actively, but it cannot eat mulberry leaves and soon starves
to death. The death of the full-grown embryo in this case is similar tothe case reported by TSUJITA (1951) of, the death of the larvae immediately after the 1st moulting.
The characteristic dead eggs may be called "lethal yellow eggs'"
These eggs resemble the eggs of the red-larva strain not only in theirexternal features in the pigmentation period, but also in the appearanceof the embryo inside the chorion. They are, however, easily distin~
guishable from the latter by their inability to hatch.
A few batches in back-cross F 1 lemon X lethal yellow, produced only
normal larvae, while the other batches (amounting to about 2/3 of thetotal) segregated normal, lemon and lethal yellow eggs in the ratio 2: 1: 1.
Also, in the back-cross lethal yellow x Ft lemon, the larvae of three types
segregated in the ratio normal 2: lemon 1: lethal yellow 1.
,17

It is well known that lemon is recessive to normal (OGURA 1922). The
recessiveness of lethal yellow to wild has been ascertained by SUZUKI(1950). The experimental results described above dearly show thatlemon .
is dominant to lethal yellow. Therefore, I could draw the following Gondusions : i) The three genes +, lem, and ly form a multi-allelic series,
and ii) their dominant-recessive relation is +>lem>ly.
The reciprocal crosses between +//y and lem/ly give somewhat different results:- When the female is +Ily and the male lemlly, the embryo
homozygous for ly becomes a normal black-colored young larva andhatches out, but in the reciprocal cross, the young larva in the egg,
which is colored yellowish brown, cannot hatch out. It is thus clear thatthe stage of death is controlled by the genetic constitution of the motherused in the crosses. Therefore, it may be said that inheritance of thelethal yellow character represents another case of maternal inheritancein the silkworm. And this special genetic behavior seems to be basedon a difference in the substances within the eggs participating in theformation of pigments, such as melanin and xanthopterine·B, as well ason the interaction between them. For the confirmation at this point theaid of biochemist is to be sought for.
The embryo and the Ist-instar larva, homozygous for the gene ly aresensitive to environmental factors, as pointed by UMEYA (1951). For example, of the newly hatched larvae of the . lethal strain (+ Ily) reared ina' chamber kept at high temperature and low humidity, more individuals
die before the 1st moulting than when they are reared at relatively low
temperature and high humidity.

.'

8. Sterility in the Silkworm due to an Abnormality
in the Bursa CoPulatrix(Report by Mitsuo TSUJITA)TSUJITA and SAKAGUCHI are now working on the genetics of sterility
found in the Nfl strain. The results obtained last year are summarized
below:The females of this strain produce almost as many eggs as those of
the normal strain. More than 90 percent of these eggs, however, are
not fertilized; the percentage is often even below l.
The results of the reciprocal crosses between the normal (N) and thesterile strain (Nfl) are as follows:
Nfl X Nfi = sterile
N x Nfl = fertile
Nfl X N = sterile

18•Judging from these resultil, it is clear that the sterility is due to some
defect in the female. Therefore, the structure of the internal sexualorgans, Le. bursa copulatrix, ductus bursae, ductus seminalis, ductus
tortuosus, glandula receptaculi, in these abnormal females has been examined; and we' have found an abnormality existing in the bursa copulatrix.
The bursa copulatrix of such a female after copulation contains a spermatophore, but the passage of this organ to the ductus seminalis is chokedwith fibrous stuff which hinders spermatozoa bundles or a single spermatozoon entering the receptaculum seminis. Variation may be seen in theamount of this fibrous stuff. When it is large, complete obstruction occurs, but when it is small, some spermatozoa may migrate into the receptaculum seminis. It is evident that the very low fertilization rate ofthis strain is due to the presence' of this substance. This fibrous stuff
may be found filling the whole space between the wall of the spermatophore and the cuticular layer of the hypodermis, but it is most abundantin the cavity in the proximal portion of the bursa copulatrix. Occasionally, even the ductus bursae or the ductus seminalis is filled with thisstuff.
As for the nature of this fibrous material, our studies have shown that
it is a product of the hypodermis of the bursa copulatrix. The cuticularlayer of the flat hypodermal cells is composed of a compact aggregationof fibrous bodies running parallel in a transverse direction. Mitochondria
seem to participate in the formation of these bodies.
As to the origin of the fibrous stuff in the lumen of the organ, it ispossible that it is liberated ft:0m the apical layer of the fibers composing
the cuticular layer, or it may be newly secreted from the apical portionof the cuticular layer. At present, the first explanation seems to be themore plausible one.
Genetical analysis of this sterility is now under way.

•9.

On the Relation of Penetrance of a Gene (or a Ge.ne-set)
Causing Malformation to Environmental Conditions(Report by Mitsuo TSUJITA)

The present report deals with some effects of the environment upon
the expression of the malformation in an inheritable crippled silkworm
strain. The deformity appears on the dorsal and ventral sides of several
segments ranging'both anteriorly and posteriorly from the 5th abdominal
segment.. The shape and degree of the malformation vary markedly
from individual to individual.

19In our previous papers on the effect of the gene causing this malformation (OMURA 1950; TSUJITA 1951), it has been stated that: i) In thecontrol lot under ordinary treatment of the. eggs, the penett:a~ce of theabnormality is about 50--70%, while under the immersion treatment withdiluted hydrochloric acid 20 hours after laying. the percentage rises to 80100%. ii) However, when the eggs are treated in an early stage with a
low temperature (15°C) to slow down the development, almost all of the
Jarvaehatched from them beoome normal.
For the purpose of accurately determining the sensitive period, TSUJITA,
in cooperation with T. T AKASU of the Sericultural Experiment Station inTokyo, examined the abnormality among larvae hatched from eggs kept
at low temperatures (15° and ZOOC) in an early stage.of development forperiod of 1,3,5 and 7 days.
A summary of the results obtained is presented. below.
(1) Eggs first kept at a temperature of 25°C f.or 10--15 hours after oviposition, were subsequently incubated at 15°C for 3 days. They werethen kept in a cold room at 5°C for 60 days. After such refrigeration
they were subjected to treatment by dilute hydrochloric acid. The rateof abnormal larvae hatched from these eggs was very low.
(2) When the incubation period at the temperature of 15°C was extended to 5-7 days, few abnormal larvae were produced.
(3) When low temperature treatment was began 20 hours after· ovipOsition and continued as in the preceding experiment, more malformed
larvae were produced than in the foregoing cases. Furthermore, delaying the beginning of the treatment with low temperature (l5°C) until 25
hours after oviposition hardly reduced the rate of malformed individuals
in comparison with the control lot.
. (4) In the ca:;e in which the temperature was changed from 15°C to
20°C, a higher percentage of malformation was obtained than in the caseof 15°C.
(5) Lastly, when the eggs were immersed in dilute hydrochloric acid
20 hours after oviposition, and incubated at 15° or 20°C for 1,3,5 and 7
days resP,ectively, almost the same tendency as that described above wasrecognized, although on the whole, more malformed larvae were produced than in the lot treated with the refrigeration·immersion method.
Even in a lot in which the eggs were treated with dilute hydrochloric
acid 20 hours after oviposition and incubated at a low temperature forseveral days, a number of abnormal larvae appeared.
It has been confirmed, by the results presented above, that the mostsensitive period of the gene causing the malformation to environmetal
factors, especially temperature or stimulation by hydrochloric acid immersion, is of very short duration, from 10 to 25 hours after oviposition. This period exactly corresponds to the 'early stages of the embryo

20

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•

'.

formation, Le. the time during which cleavage nuclei migrate under theegg shell, form an epithelia! layer, and some of them begin to invaginate and differentiate into the blastoderm.
Also, we have obtained results which suggest a correlation between thetemperature in the pupal stage and the percentage of abnormality in thenext generation. We shall, however, defer the detailed report on thispoint to the time of completion of th~ experiments.

10-. The EjJet:t of Centrifugal Force uPon the DevelaPnwnt
of Silkworm and Eri-Silkworm Eggs
(Report by Bungo SAKAGUCHI)•

A. Induction of malformations
Experiments are now in progress to study the malformations inducedby centrifuging, as a preliminary to an investigation of the embryological genetics of various malformations. One to 40 hours after oviposition,
eggs were subjected to centrifugal f~rce of 4,000 R.P.M. for 10-15
minutes, or of 10,003 R.P.M. for 15-30 seconds. All eggs were placed
10 cm from the axis of rotation.
The results obtained with the silkworm (Bombyx mori) were similar
to those with the eri-silkworm (Attacusricini).. In this report mainly
the results of experiments with the silkworm are described.
When eggs were centrifuged, 20 hours after oviposition, the induced
malformations amounted to 28%, which was the maximal value. This
seems to show that the stage 20 hours after oviposition which corresponds to the time of blastoderm formation is the critical one. Wheneggs before or after this stage are treated, the rate of malformation ismore or less reduced according to the variation in the time factor. ~x~amination of the embryos in dead eggs has shown that the earlier thestage when the c.entrifugal force was applied, the more abnormal embryos were produced.
The induced malformations included segmental malformations, Le. fusion of several segments apparently restricted to the superficial part ofthe body, defects in some organs, twisting of the longitudinal axis of thelarval body, duplications of some organs, and asymmetry of thoracic
and abdominal organs.
Genetically abnormal strains give more abnormal larvae by treatment
than the normal strain. The abnormality tends to be localized aroundthe fifth, sixth and ninth segttlents. There is some resemblance between
the types of malformations indu~d by centrifugal force in the n<~rmal
sttainand those in certain ge~tically malformed strains. The type of21•

deformity bears a close relation to the direction of the· centrifugal force
upon the eggs.
B. Embryological observations
When· eggs are subjected to the centrifugal force 5 and 10 hours ·after
oviposition, deformity appears in various organs of the developing embryo. For instance, thoracic legs, mandibles and antennae are formed
at abnormal sites. This seems to be due to the fact that the predetermined regions of the organs are thrown into confusion by the centrifugal
force, and that abnormal differentiation proceeds in this confused state.
The eri-silkworm· embryo has shown more abnormalities than the silkworm embryo.
In one of the eggs treated 5 hours after oviposition a dwarf embryo
was formed at the region opposite to the micropyle; Le., near the posterior pole, lying parallel with the shorter axis of the egg. In anotherembryo, some organs showed striking abnormalities ; for instance, themandibles had the cutting margins turned outside, and they were fusedwith each other at their bases. Thus the direction of the mandibles wasreversed as compared with that in the normal condition.
•
In another egg treated 5 hours after· oviposition, an imcompletely
double embryo was formed, apparently by splitting . of the longitudinal
axis of the embryonal body. Also, embryos having duplicated organs
have been found. These results seem to indicate that the ooplasm· has acertain regulating power in the formation of the embryo, as well as in
the differentiation of organs. This tendency is more marked in the erisilkworm than in the silkworm.
It is interesting that in eggs treated one hour after oviposition, appendages like mandibles, antennae, thoracic legs, etc., developed independently of one another, until the pigmentation period. This observation· suggests that the development of such organs proceeds to a certain degree
independently in each of the segments. This tendency was recognized
more clearly in the silkworm embryo than in the eri-silkworm embryo.

D.

GENETICS OF POLYMORPHISM IN SOME
INVERTEBRATES(Report by Taku KOMAI)

1. The Lady-beetle Harmonia
Population samples of the variable lady·beetle Harmonia have beenobtained from ten localities of Hokkaido. This collection has been madeunder the expectation that some samples might show evidence of their•resemblance to the population on the Asiatic Continent. None of them,
however, did. But two samples from Kenbuti near Kamikawa collected
at different seasons showed considerable difference in composition, reminding one of the situation in another polymorphic lady-beetle A.dalia
biPunctata reported by TIMOFEEF~' some years ago from a suburb of
Berlin. More materials are being sought from the same locality.
A more recent sample from Suwa shows a distinct directional change
in composition which has been continuous since 1920. An attempt to
explain this change in :relation to climatic change is under way. Also,
experimental studies on the differential viability of various color types ofthis species under low temperature are in progress.

2.

The Lycaenid Butterfly Neozephyrus

The Lycaenid butterfly Neozephyrus taxila japonicus, which is rather
common in the mountainous districts of Japan, shows a great sexual
difference in the color of the wings. Moreover, the female is tetramorphic:
1. dark-brown without any marking, 2. with orange patterns on theforewing, 3. with bluish suffusion on the forewing, 4. with both orange
and bluish markings. These four forms are apparently due to a set of
triple-allelic genes, something like the four blood-types in man, i.e., thegenes producing the markings in the second and third forms are both
dominant over the gene producing the plain form, while the fourth form
is the heterozygote of these dominant genes. Ten population samples fromdifferent localities sustain this view. In nearly all of these samples, however, the second and third forms are somewhat lower, and the first andfourth forms higher in frequency than could be expected on this view.
This is probably due to a relatively lower viability of the dominant homozygotes, as compared with the dominant heterozygotes and recessives.

3.

The Pierid Butterfly CoNas

Colias hyale poliographus is one of the commonest butterflies in thefields of Japan. As in most of the other species of the same genus, thefemale shows two color forms, white and yellow. The white form iscommoner than the yellow form over the whole range of this species inJapan. S. AE, a student in Kyoto University, has performed breeding
experiments on this butterfly under KOMAI'S direction. He has found thatthese two forms among the females are due to a set of allelic genes, W
and w, of which the dominant gene W shows its effect only in the female;
all males are yellow, irrespective of their genic compositions. Thus, thegenetic behavior of this species is essentially the same as that of theallied American species, C. chrysotheme studied byGERouLD and HOVANITZ.
A difference may be found in the fact that, while in the American species

23the dominant homozygote WW is apparently lower in viability than either
the heterozygote Ww or the recessive homozygote ww, in the Japanese
species the recessive ww seems to be more handicapped in natural selection than either Ww or WW. Several pop'llation s'lmples from various
localities in Japan and Korea sugg~st the existence of a geographic
gradient in the incidence of these genes.

4.

The L~nd-sn,:lil Bradybaena

The common small land-snail Bradybaena similaris has four color
forms-yellow-plain, yellow-striped, brown-plain and brown-striped. The
basic genes of these forms are triple-allelic: the yellow-plain is the recessive form; both the striped and brown are dominant forms; while brownstriped is due to the combined effect of the two dominant genes. Morethan 8) samples from different localities in Japan show a different relative
incidence of these genes. They also indicate the strong effect of isolationon the differentiation of local populations. Comparison of samples ofliving and dead shells from one of these localities suggests a relatively
higher viability of the recessives and the dominant heterozygotes over thetwo dominant homozygotes. Experiments are under way, using a refrigerator to test the relative suscestibility to low temperature of these
forms.

E.

GENETICS OF SOME CEREALS(Reported by Seiji MATSUMURA)

1. Radiation Genetics in Einkorn Wheat

Dormant seeds of Triticum monococcum were exposed to X-radiationof 18JKVP, 3mA, 16cm, without a filter. The doses ranged from 5,400
to 13,500r units. The higher the dosage, the greater was the delay inthe germination of irradiated seeds and the growth of the seedlings. The
frequency of chromosome aberrations increased in a parabolic relation to
the dose.
At the same dose (8,100r) and target distance (16cm), but with varying
kilovoltage (BO-180KVP) and time of exposure, the aberration frequency
decreased with the increase of wave length.
As to the relation between the aberration frequency and the dose orwave length, the results of previous experiments at 30-90KVP (MATSUMURA
1951) have been confirmed. These facts can be explained on the basis of
the difference in ionization distribution within nuclei and chromosomes.
The mutation rate of chlorophyll abnormalities among the seedlings ofthe X 2 generation seems to depend not 'only upon the X-radiation dosage,

24.,

but also upon the wave length. The final decision on this relation will
be deferred until after obgervation of the mature plants has been made.
Dormant seeds of the same species were also exposed to short electric
waves and supersonic waves. Few irregularities were observed in themeiosis of the treated plants. Among the progeny obtained by selfingof the treated plants, however, there have been found some abnormal
plants-highly sterile or dwarfish or haploid. The mechanism of the
production of these abnormalities awaits further investigation.

2. Nullisomic Dwarfs in Vulgare Wheat andGigas-plants in their Offsprz·ng

ItDwarf plants possessing 20rrchromosomes occasionally appear among
the offspring of pentap'oid wheat hybrids. These plants are nullisomics,
deficient in a chromosome pair from the D-genome. The seven different
kinds of nullisomics may be called a-g-dwarfs. Dr. SEARS recently
obtained all the 21 possible nullisomics in Triticum vulgare (Chinese
Spring). He has been working on the study of crosses between his own
nullisomics, XV-XXI, and the author's a-g-dwarfs. His results showthat NuUi-XVI corresponds with the g-dwarf. The author's crossing experiments, however, show that chromosome XVI can correspond to noother chromosome than the f-chromosome, as the hybrid Nulli-XVI x fdwarf is highly sterile (fertility, 2.94%) and has chromosome conjugations
mostly of the type l m +18 n +1 r and 20 n • while NuUi-XVI x g-dwarf has
a relatively high fertility (73.04%) and the chromosome configuration isof the type 19n +2 r +frag. (The fragment has been derived undoubtedly
from the. g-dwarf used in the cross.) Among the F 2 of the former
hybrid, most of the plants are dwarfish; only a few have normal height
and the chromosome configuration, 20n +1 r. Among the F 2 of the latterhybrid, on the other hand, many plants are of normal height and only a
few are dwarfish.
The hybrids between Nulli-XVI and a-e-dwarfs usually have thechromosome conjugations 19u+2r, 1nr +18 n +1 r, 18n +4r, 1m +17n +3 r etc.
and high fertility. But the hybrids of Nulli-I, -III and -VII with a-gdwarfs are of lower fertility, in spite of showing similar chromosome
conjugations. This must be due to the fact that in the former hybrids
the A- and B-genomes are complete, and only two of the D-chromosomes
are without partners, while in the latter hybrids either the A- or B-genome,
and also the D-genome, are lacking in one chromosome.
In the hybrids between Nulli-I or -VII and a-g-gigas-plants, the chromosome configurations of 1rv+18n+1r, 1m+18n+2I, 19n +3 I and 20 n +1 I
have been observed. The hybrid Nulli-I X c-gigas was highly sterile(fertility, 4.94%), while the hybrids between Nulli-I and other gigas-plants
had 65-87% fertility. Furthermore, the hybrid Nu1li-VII~a-gigasshowed25

a markedly higher fertility (84.60%) than the hybrids between Nulli-VIIand other gigas-plants, whose fertility was 20-45%. From these results
it is assumed that the supernumerary chromosome a in the a-gigas is thesame as SEARS' VII. The hybrid Nulli-VII x a-gigas is expected to showa higher fertility after the recovery of the chromosome in which the A·or B-genome of SEARS' nullisomic is lacking.

•

3. Studies on Agropyrum, a Genus Related to Triticum
Of the hybridization experiments between Triticum spp. and AgrojJyrum
spp., the one between T. polonicum (AABB) and A. glaucum (2n=42)
has been successful. This hybrid has been cytologically examined.
Meiosis shows 5-10 gemini with the mode at 7. Often 1-2 trivalents arefound and rarely 1 tetravalent occurs. It is inferred from these facts, aswell as from earlier results (MATSUMURA 1949), that the genome of A.
glaucum which is homologous with one of the Triticum genomes is the
B-genome. The hybrid is perennial and vigorous, but completely sterile,and matures very late.

4. Morphologically Different Twins found in the Progenyof a Hybrid Wheat(Reported by Taro FUJII)

Twin plants of 2x: 2x-chromosome set are morphologically identical.
In the F 2 of a hybrid between Nulli-VII (2n=40) and a-gigas (2n=42) apair of twin plants was obtained. They both had 41 chromosomes, but
one of them was awnless and the other tip-awned. In the selted progenyof each of these plants there appeared many normal plants with 21 II and2011 + 11 besides a few dwarfs, whose chromosomes should be 2011 • The
offspring of the awnless twin were all awnless. The tip-awned twin
showed relatively lower fertility and a lower percentage of heading. Its
progeny segregated as to the awn character in the monohybrid ratio, 1
awnless; 2 tip-awned; 1 awned, independently of chromosome numbers.
This shows that the tip-awned twin must have been heterozygous as tothe awn character.
The origin of these twins can be explained in two ways:
1) One fertilized egg (awnless homozygote) was divided into two embryos in an early stage and a minute deficiency of the awn gene occurred
simultaneously.
2) The egg cell and one synergid were fertilized by 2 pollen grains,
one with the gene for awnless and the other with a minute deficiency of
the awn gene.
The first hypothesis seems to be more probable than the second.

26

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•

F. GENETICS AND CYTOLOGY OF NICOTIANA
1. Cytogenetic Studies on the Genus Nicotiana II(Report by YO TAKENAKA)•

A. On the meiotic chromosomes of ten wild and one cultivated sPeciesof the genus Nicotiana
Seed of eight species, namely Nicotiana longiflora, N. paniculata, N.
tomentosiformis, N. trigonojJhylla, N. undulata, N. suaveolens, N. Gossei
and N. rotundifolia, were received, together with other wild species, fromProf. R.E. CLAUSEN, through Dr. F.A. LILIENFELD, one of the collaborators
in our Institute. Three other species of the same genus were obtained
from Japanese sources. Seeds of N. nudicaulis were obtained from theKagoshima Tobacco Laboratory, Japan Monopoly Corporation. N. alala
is found growing wild, since about 20 years ago, in the fields of KonoGakuen near Misima. N. rustica is being cultivated in the Hatano Tobacco
Experiment Station.
The behaviour of chromosomes and the number of gemini wereobserved in the meiosis of the pollen mother cells of these eleven species.
The bivalent chromosome numbers are as follows :-N. alata 9, N.
longiflora 10, N. paniculata 12, N. tomentosiformis 12, N. trigonophylla 12, N.
undulata 12, N. nudicaulis U, N. rustica U, N. suaveolens 16, N. Gossei
18 and N. rotundifolia 22. These numbers agree with those given by
previous authors, such as GOODSPEED, RESENDE, TENOVSKY and WHEELER.
The meiotic figures have been found to be very regular, except that it has
been difficult to count 24 gemini in the 1st metaphase of N. nudicaulis,
since some chromosomes present. figures resembling quadrivalents.
B. Cross between N. glutinosa and N. sylvestris
In the summer of 195'), 266 flowers of N. glutinosa were pollinated byN. sylvestris and gave 34 capsules. The reciprocal cross, 418 flowers ofsylvestris pollinated by glulinosa, gave no capsules. Almost all of theseeds were abortive, and only 22 plants were obtained in the spring of1951. Twenty of these showed the typical features of glutinosa and grew
to maturity in the same manner, like the control glutinosa plants. Of theremaining two plants, one was wholly sylvestris, and the other was very
dwarfish, looking like a haploid sylvestris produced by androgenesis,
although the leaf shape showed some features of glutinosa. This dwarf
plant died before blooming so that its meiosis could not be examined; itsroot tips showed 24 chromosomes. This shows, at least as far as theroots are concerned, that the plant was not a haploid sylvestris. It may
have been a hybrid between glutinosa and sylvestris.
The production of relatively many plants of the gluit'nosa ty}:e in the
cross described above may be due to the considerable dissimilarity betw€en27

the genomes 01 gtutinosa and sylvestris, which made the nuclear fusion
extremely difficult, so that the glutinosa egg cells developed parthenogenetically by chromosome doubling, after activation by the pollen
hormones of sylvestris. Or it is possible that parthenogenetic development was induced through fusion of an egg cell with the synergidal cellin the same embryo-sac. For the production of the sylvestris type plants,
it may be assumed that one sperm nucleus with a doubled chromo:iomenumber or two fused sperm nucl~i developed androgenetically into asylvestris embryo within a glutinosa embryo-sac.
C. Hybrz'd between N. glauca and N. Plumbaginifotia
Pollinations of many flowers of N. glauca with pollen of N. plumbaginifolia gave only 6 capsules in the summer of 1950.
Many F 1 plants were obtained from this cross. Although they weregenerally intermediate between the two parents as to external characters,
the shape of leaf and branch approached those of the father and, on thecontrary, the height of the plant came nearer to that of the mother. The
flower size was intermediate and the flower colour was at the start lightyellow resembling that of glauca, changing to pale white approaching that ofptumbaginifotia at the end of the flower life. Leaves, flowers and branches ofthe plants were very numerous, the growth was extremely exuberant andthe "flowering period very long. In short, the plant showed typical heterosis.
The somatic chromosome number, as expected, was 22, containing 12
chromosomes of glauca and 10 of plumbaginifolia.
The meiosis of the pollen mother cells was highly irregular, as is
generally observed in hybrids between distantly related species. In thefirst metaphase, many univalents were observed besides 1-4 bivalents, but
the partners of the bivalents seemed to be only partially homologous,
because their connection was loose. In the first anaphase, chr mosome
bridges were very frequently observed, and some of them were carriedover to the lInd anaphase or the tetrad stage. There were also new
chromosome bridges which appeared only in the lInd division. The lInd
division was carried through in most of the pollen mother cells, but wasobserved to break down in a few of them. In the tetrad stage, manymother cells held four mierospores in each cell, a few cells held only one,
two or three microspores and some of the mother cells contained a few
small microspores besides the microspores. Because of the irregularmeiosis, this hybrid did not give even a single seed.

2.

Cytogene#c Studies on the Genus Nico#ana III(Report by Yo TAKENAKA and Flora A. LILIENFELD). By crossing two commercial varieties of N. tabacum, Bright Yellow
and Odaruma, with N. sylvestrz's, one of the original parents of N. tabacum,28

triploid hybrids were obtained in 1950.
Morphologically the hybrids could scarcely be distinguished from N.
tabacum. However, they blossomed ten days earlier than N. tabacum.
Because of this feature they could become important under conditions
which require early maturing tobacco varieties.
The meiosis was studied in pollen mother cells. As expected, thechromosome conjugation was 12II +12J, the univalents representing thetomentosa set. From the occurrence of trivalents it could be concluded
that several of the tomentosa chromosomes are semihomologous with thesylvestris chromosomes. Most of the nuclear plates showed the configuration 3m+9II+9I. According to expectation based on the irregularbehaviour of the chromosomes after first metaphase, only a few seeds
were obtained.
«3.

Mutations in Tobacco Induced by X·rays(Report by Seiji MATSUMURA and Tara FUJII)"•

Dormant seeds of Nicotiana tabacum (Bright Yellow) were subjected to
X-ray treatments. In the first experiment, the seeds were e.xposed tounfiltered radiation at 90KVP, 3mA, 15cm, of intensity of 216 r/min for
10-60 minutes. The dosage applied ranged from 2,160 to 12,960 r units.
There were no striking differences in germination rate of seeds or inmorphological characters of mature plants between untreated and variously
irradiated plants.
In the second experiment, the seeds were irradiated with harder X·rays
at 180KVP, 3mA, 11.2cm, without filter, of 480 r/min intensity. The
dosage was 5,000-50,000 r. At the highest dosage the germination rate of
the irradiated seeds was reduced, from the 82.4% of untreated seeds, to65.6%. The higher the dosage above 20,000 r, the more delayed anduneven were the germination of treated seeds and the growth of theseedlings. Among the mature plants from seeds irrcrdiated at 15,000 rand
at higher dosage, various kinds of abnormalities appeared, such as narrowleaf, crepe leaf, white spotting, etc. In some of the plants the capsules
dropped after flowering. At 5c),OJO r, about 40% of the Xl-plants showedsuch abnormalities. Chromosome aberratIOns, such as l IV +22u and 24u+frag. etc., were observed in the meiosis of these plants. The relationof aberration frequency to dosage is not clear, because of the small
number of anthers examined.
44 offspring were bred from the selfing of Xl-plants in the first experi·ment. In 15 of them mutants in morphological characters appeared,
such as: early and late maturity, vigorous, early bolting, dwarf habit,
broad leaf, narrow crepe leaf, spotted leaf, etc. Some of the mutations
showed characters useful for breeding purposes.
29

4. Studies on the Relative Weight of Mid-rib in Nicotiana
tabacum Leaves(Report by Kan-Ichi SAKAI, Kanji GOTOR and Shinya Iy AMA)

The proportion of mid-rib volume to the total volume of a tobacco leaf
is not only important to the tobacco industry but also interesting to thestudents of quantitative characters in plant genetics. With the purposeof analyzing the genes controling this character, our first attempt wasmade to examine the differences of that proportion in various tobacco
varieties as well as its correlation with some other leaf characters. The
mid-rib proportion was determined by the ratio of4mid-rib weight to total
leaf weight.
Five individuals were taken at random from each of twenty·four
tobacco varieties and from three F 1 hybrids. From each individual fourleaves, from the third to the sixth leaf upwards, were collected. Twoleaves, the third or the fourth and the fifth or the sixth were measured
as to their mid-rib proportion as well as their shape and size immediately
after han;esting. These· two and the remaining two leaves were thendried at room temperature and again the mid-rib weight and total weightof dry leaves were determined.
Results of the analysis of variance of the data are as follows:
Variation d.f.
due toMi~~i~ pl."0IJorti~n-IIVaria.t io-;--tLf. Le:;-~-izel) Leaf shape2)

Fresh leaf

Dry leafll due to,I

Y:Ji~i%al 1~~8fif-~7~)r~il_

i::~e~~_ 2~f-:;---~g:~~~~** Exceeds the 1 percent point.
I) (Length of mid-rib) x (Width of leaf).
2)(Width of leaf)/(Length of mid-rib).

.

The correlation coefficients between the mid-rib proportion of dry leaves
and that of fresh leaves as well as size and shape of leaves are as follows:
Mid-rib proportionof dry leaves------ ---------~_.

------

Mid-rib proportion of fresh leaves
Leaf-size
Leaf-shape* Exceeds the 5 percent point.

-----+0.913**+0.282-0.455*** Exceeds the 1 precent point.

The conclusion that the mid-rib. proportion in dry leaves is highly
correlated with that in fresh leaves offers valuable information for our
future work.

30

..

G.

GENETICS OF CAPSICUM

1. Genetic Studies on some Fruit Characters in Capsicum annuum(Report by Kan-Ichi SAKAI)

Comparative studies were made in Capsicum annuum on some fruit
characters of F 1 hybrids and their parents. The" experiment consisted of
two parts: 1. comparison between the effects of different paternal genotypes on F 1 hybrids derived from a common mother-plant, and 2. studyof the behavior of genes for fruit characters. The number of progeny
obtained from selfing and crossing in these two experiments approached
one hundred, and the experiments were combined in order to apply thesimple lattice design with four replications.
Though data obtained on the average weight of a fruit, number offruits per plant and the total weight of fruits per plant are still under
examination, the following results can be considered as established:(1) The total weight of fruits per plant exhibits heterosis in somecombinations and not in others.
(2) The smaller number of fruits per plant behaves in most cases as
an incompletely dominant character.
(3) Also, small fruit size is partially dominant over large fruit size.
Further discussion and criticism will follow after the necessary computations have been completed.

2. D2Cline of Fruit Productivity by Artificial Selfing
in Capst'cum annuum(Report by Yasuo SUZUKI)..

With four strains representing three varieties of C. annuum, the writer
made comparative studies on fruit productivity by means of open-pollination and artificial s3lfing. The experiment was conducted by the splitplot design with three replications. Data obtained were analyzed by using
the variance-analysis method. Significant differences between open pollination and selfing have been found in the total number of fruits, the total
weight of ripe fruits, the topweight, and in the total weight of ripe andunripe fruits. The writer, however, has failed to find any significant
difference between the treatments in respect to the number of ripe fruits,plant weight excluding fruits, and in the average weight of fruit.
Variety-treatment interactions in these four characters except plant weight,
the total weight of ripe fruits, and the total number of fruits were also
non-significant. The t-test of data has shown that the decline of character
due to selfing in all but the average weight of fruit was apparent only in31the Chinese variety. Thus the rate of increase in the yield characters has
proved to be apparently different between varieties with smaller and thosewith larger fruits, the increase in the former varieties being 3 to 9 per
cent, while that in the latter bearing large fruits such as the Chinese
variety ranged from 35 to 60 per cent. The increase was apparent in thenumber of fruits and in the other characters, except the average weightof fruits. Quantitative differences in yield characters between open- andself-pollinated lots in this experiment are possibly due to heterotic genes
which would segregate within the same variety. Further experiments
will be conducted in 1952.

H.

GENETICS OF EGGPLANT(Report by Kanji GOTOH)

1. Studies on Dzvelopmental Processes of ~Fruits in Eggplants
The fruit-shape in eggplants is roughly classified into spherical, oval
and long. The purpose of this investigation is to clarify the developmental
processes of these different fruit-shapes.
Two varieties and several F 1 hybrids between these two and othervarieties with different fruit-shapes were examined. From seven days
after anthesis the longitudinal and horizontal diameters of the developing
fruits were measured on every fourth day until they became almost
constant.
The data show that the so-called fruit-shape expressed by the ratio ofthese two diameters became stabilized from 15 to 23 days after anthesis.
The regression equations and the regression coefficients concerning thedevelopmental process in all the F 1 and the varieties were computed fromdata transformed into logarithms on each diameter. The regression
coefficients thus obtained are all statistically significant. Then the differences between the regression of F 1 and that of its parents, as well as
the difference between the regression::; of the parents themselves wereanalyzed by joint regression methods.
A comparison between these regression equations suggests that in somecases differences in increments of longitudinal or horizontal diameter had
already been established before the measurements, since their differenceswere statistically significant. In one case, the differenc of regression
coefficient in horizontal diameter between on F 1 hybrid and its parent
was found to be statistically significant.
In addition, the growth curves of these dimensions suggest the existenceof inherent turning-points. When the growth of fruit attains turning32..

points, the ascending tendency of growth rate begins to decline. Conse-'
quently, it is conceivable that all growth curves have two turning-points,
one before anthesis and the other at a certain period after anthesis. Also
it is likely that differences found in the shape of fruits are due to integrated
effects of the genes acting in different periods partitioned by these twoturning points. Hence, the genetic analysis of fruit-shape has to be conducted with reference to each of these three stages.

2. Regression Analysis of Fruit-shape and -size Genes
with the Aid of F 1 Hybrids in Eggplants
In eggplants the shape and size of fruits are highly variable. An
investigation was undertaken to analyze the role of genetic factors concerned in the variability of these quantitative characters. Five varieties,
apparently diff~rent in their fruit characters, and their F 1 hybrids weregrown in a randomized block arrangement. Measurements of thesecharacters were made simultaneously, when the fruit seemed to have completed development about a month after anthesis. Arithmetically calculated
data were obtained on fruit-shape and -size. The shape was expressed by
the ratio between the length aI1d width of the fruit, and the size, by theweight per fruit. G~notypic variance, variance due to dominance andcovariance between F 1 and its variable parent were calculated in each of
the five constant parent groups. By means of constant parent regression
analysis, mathematical mo:iels of the action and effect of fruit-shape and-size genes were obtained.
,By this means it has been found that there are arithmetically cumulative
action with slightly negative dominance of the genes for shape, andlogarithminlly cumulative action of the genes for size.

3. Studies on Combining Ability in Eggplant Varieties•tThis experiment was undertaken to ascertain whether general or specificcombining ab:lity existed in eggplants. 10 varieties and 15 F 1 hybrids
between them were examined by replicated yield trials in a randomized
block arrangement, and the results were tested statistically.
The yield of the F 1 hybrids was, as a whole, superior to the mean yieldof their parents. In 14 combinations, the F 1 hybrids outyielded the loweryielding parents and in 5 combinations they even outyielded the higheryielding parents, the difference being statistically significant.
The increase in yield of the F 1 hybrids over the mean yield of theirparents ranged from 12% for the Minden x Sendai-naga No. 1 to 70% for
BurmaxSendai-naga No. 1. The F 1 hybrids between the variety
Turuboso-sen-nari and any other variety were very vigorous and showed
higher yielding ability as compared with other combinations. This suggests

33that the variety Turuboso-sen-nari has a high general combining ability.
Hybrid vigor obtained in hybrids between Turuboso-sen-nari and Sendainaga No. 1 or Sinkuro, etc. also suggests that some of the varieties havespecific combining ability.
All F 1 hybrids from these combinations outyielded the higher-yielding
parents and the differences were highly significant.
Furthermore, it has been shown that the high yielding varieties do notnecessarily have high combining ability, and that the increase in yield of
the F 1 hybrids outyielding the higher yielding parent is largely due to anincrease in the number of fruits per plant.

1.

.

CYTOLOGY AND GENETICS OF SOMEFLOWERING PLANTS
1. Karyological Studies on Narcissus

I(Report by YO TAKENAKA)

Karyological studies, especially karyotype analyses, on the genus
Narcissus have been carried out, and somatic chromosome numbers of 58
clones including forms, garden and wild-growing varieties, belonging to
10 species, have been determined as given below.
(1) Group of Narcissus Tazetta L.
Mont cenis 20, Maestro 20, Jaune Sprene 30, Batharst 20+1 fragment,
Paper White 22, Grand Monarque 32, Runa 32, White Pearl 32, Sicily
White 32+1 fragment, Gloriosa 17, and var. chinensis 30 and 32.
The basic haploid chromosome number of this species is 10. Diploid,
triploid and aneuploid plants were observed.
In one garden variety, "Gloriosa", 17 som'ltic chromosomes w~re counted
in the root tips, suggesting its hybrid origin from a cross between N.
Tazetta with 10 and another species with 7 as the haploid chromosome
number. The latter parent may have been N. poeticus, judging fromthe appearance of this variety.
(2) Group of N. poetaze hort.
Klondyke 17, Aspasia 17, Triumph 24, Alsace 24, and Erbira 24.
This plant is considered to be a horticultural species originating fromthe hybridization between N. poeticus var. ornatus and N. Tazetta. The
chromosome complex of his group consists of one chromosome set of
N. Tazetta and one or two sets of N. poeticus.
(3) Group of N. poeticus L.
Almira 14, Ornatus 21, King of England 21, Pheasnt's Eye 21, and var.
plenus 14.
The basic haploid chromosome number is ~, diploid and triploid clones
have been found in this group.
34

.

I

..

•

,

(4) N. ]onquilla L.
Jonquill Single 14.
The basic haploid chromosome number is 7.
(5) Group of N. odorus L.
Odorus Regulosus 14, Campernella Common 14 and Odorus Giganteum 28.
The somatic cells of this group have 14 chromosomes as the basic diploid
chromosome number. A tetraploid clone has been found.
(6) Group of N. incomparabilis L.
Gloria Mundi 14, Sir Watkins 21, Fire Flame 21, Bedouin 21, Will Scarlet 28 and Bernadio 28.
The basic haploid chromosome number is 7.
Diploid. triploid and tetraploid garden varieties have been found in thisgroup.
(7) Group of N. Barrii hort.
Barbara Holms 21, Conspicuous 21 and Barrii Seagull 21.
It is considered that this species arose from a cross between N. incom·
parabilis and N. poeticus.
Three clones examined were all triploid.
(8) Group of N. Leedsii hort.
Minnie Hume 14, Amabilis 21 and White Lady 21.
This horticultural species is said to have originated from N. incomparabilis x N. poculidormis. Three clones examined were diploid or triploid.
(9) Group of N. Pseudo-Narcissus L.
William Gold Ring 14. Vanilla 14, Princeps 14, Golden Spur 14, Cervantes 14, ].B.M. Cum 21. Emperor 21, Victoria 21, Empress 21, Van
Waveren';; Giant 21, Madam Plemp 21+ 1 fragment, Silver Spur 28, King
Alfred 28. Glory of Noordwijk 28, Madame de Graaff 31. Tresserve 36.
Of the clones belonged to var. pleno, Silver Wing 14, Orange Phoenix
13+ 1 fragment, Double van Sion 14 and Sulpher Phoenix 14.
The basic haploid chromosome number in this group has been observed
to be 7. This group constitutes an euploid series of2 x, 3 x. 4 x, and5.x, with the addition of a few aneuploid plants and two clones with achromosome fragment.
(10) N. Bulbocodium L.
Only one clone was examined; the somatic chromosome number was
42, consisting of 6 basic 7-chromosome sets.
2. Cytogenetic Studies on the Sex in Cannabis sativa L. I
(Report by YO TAKENAKA)

One spontaneous autotetraploid female plant was found among about
300 hemp plants from seeds sown in our garden in spring of 1950. In
35November of the same year, this plant gave 105 seeds, all of which were
supposed to be triploid.
The seeds were sown in our garden in the early spring of 195~. Many
seedlings withered because of lack of proper care during the long hot
season, but 50 plants grew to maturity and consisted of females, intersexes and males in the ratio of 21 ; 25 ; 4. The intersexes ranged gradually from practically wholly female plants with only a few male flowers
to predominantly male plants.
The somatic chromosome complement of hemp is known to consist of
20 chromosomes; i. e., 18a + 2X in the female and 18a + X + Y in the
male. Accordingly, the tetraploid female should have 36a + 4X, and consequently, plants with 27a + 3X and 27a + 2X + Y could have been expected as the result of free pollination of the tetraploid female. Roottips of seven plants among the offspring were cytologically examined.
Almost all cells showed thirty chromosomes as expected. In the triploid
females the X-chromosome could not be identified, but in the triploidintersexes one large chromosome of a ]-shape rather than a V-shape wasinfrequently distinguished from the other chromosomes.
The meiosis of the triploid intersexes was examined by BELLING'S acetocarmine method. In the zygotene and pachytene stages, some chromosomes were found to be arranged in juxtaposition, by threes. Also, inthe diplotene stage, three chromosomes were frequently gathered in agroup, though not necessarily parallel with one another. In diakinesis,
four to six trivalent chromosomes were found; rarely fewer than four.
Their number in the Ist metaphase was usually six. Accordingly, mostof the nuclear plates of that stage had the chromosome configuration
6111 +411 +41 • One of these trivalents showed frequently difference ofsize among its three elements, the complex usually forming a straightline by the end-to-end union of the chromosomes, though it wasoccasionally V-shaped. This tripartite chromosome may represent the
sex-chromosome's complex. The chromosome separation at the Ist
anaphase is not so irregular as is usual in other triploids, though rarely
a few chromosomes may be located outside of both polar groups.
Accordingly, at least one complete autosome set goes to each pole,and the sex chromosomes separate as X-XY, or XX- Y. The chromosomes split in the stage from the Hnd metaphase to anaphase, andgo to the poles, except for a few which are irregularly distributed
outside of the spindle at the Ist division. The number of microsporesof the tetrad stage was mostly four in each mother cell. In addition,
one or two small microspores might be found. The relative frequencyof the cases (4 microspores); (4 microspores + one small microspore);(4 microspores + 2 small microspores) found in each mother cell is about
160 ; 27 : 4. Most of the pollen grains appeared normal. As mentioned
36

•

•

above, since the meiosis of these triploids is not so irregular as in manyother sterile triploids, an abundance of seeds could be harvested from thetriploid females and intersexes.
3.

Irregular Mitosis in some Clones of the Genus Colchicum(Report by YO TAKENAKA)•"

From the observation of somatic nuclear divisions in root·tips of someclones of the genus Colchicum, the following facts have been confirmed :(1) Somatic chromoilome numbers-Paplium major 2n=34, Autumnalealba 2n=36, Ancrist 2n=38, Purpurea 2n=38; one clone from the Botanical Garden of Hokkaido University had 2n=40. The same clone,transplanted in 1927 into Dr. OGUMA'S garden in Sapporo from the Botanical Garden of Hokkaido University and retransplanted in 1950 to ourgarden in Misima surprisingly showed 2n=38.
(2) In general, the mitotic chromosome figures. of all these plants
showed stickiness, being" C-mitotic", and it has been difficult to determine exactly the metaphasic chromosome numbers, as the mitotic figures
almost always show fragmentation and/or fusion of chromosomes.
(3) The clone transplanted to Misima from Dr. OGUMA'S garden in
Sapporo showed the greatest irregularities of all. This clone had produced
normal flowers every autumn all through the 21 years from 1927, exactly
like the original clone in the Botanical Garden of Hokkaido University.
But in the autumn of 1950, all the plants in Misima had open degenerate
flowers entirely lacking stamens and petals, though having normal pistils
and corollae. Root-tips of one of these plants were fixed at the end of
the summer, 1950. The sections showed various irregular mitotic figures.
(a) There were many necrotic cells in the cortex region apparently
resulting from extremely abnormal diffusion or contraction of chromosomes. At the same time, abundant chromatin bodies of various shapeschromosome clumps, fragments or chromatin granules-were spread out
into the cytoplasm. (b) Some anaphasic figures showed unequal distribution of sister chromosomes to the poles. (c) The equatorial plates held
mostly 38 chromosomes, but not infrequently various numbers of chromosomes from 34 to 41 were seen. The largest V-shape chromosome
was usually represented twice in each nuclear plate, but there weresometimes three of them.
These findings, especially on the clone derived from Dr. OGUMA'S garden, seems to allow the following conclusions:(1) The plants of the genus Colchicum are very strongly affected byenvironmental conditions, which is shown in the frequency of irregularnuclear divisions. Such a reaction may have some relation to the c<;>lchicine contained in the tissue of the plant.

37

(2) A new clone having a different chromosome number or a different
karyotype, or both, may be produced from the original clone, as a consequence of various differentiations in the number or shape of the chromosomes in the meristem cells of a bulp, if such a change takes placeeven in a single cell, and also it takes the precedence in competition withmany other cells. The abnormal clone described above seems to be an
example of this kind.
(3) Series of very unusual chromosome numbers in this genus, reported by LEVAN (1940), such as 2n=38, 40, 42 and 44, may have been derived from a single ancestral pattern.

..

4. Progeny of Lycoris radiata(Report by Hitoshi KIHARA and Flora A. LILIENFELD)

Seeds of the triploid Lycoris radiata, obtained from selting and fromcross-pollination with pollen of the diploid L. sanguinea, were sown immediately after ripening. The results of self- and cross-pollinations areshown in the following table.
Table 1. Results of self- and cross-pollination experimentswith L. radiata

I No. of in- I No. of
I No. of I No. of I No.. of gerI florescences
flowers
fruits good seeds:~~t~)

self-po-ll-i~-~-~---:-I- --;:----I--~-----I--------I---~;~--!~--~--

Cross-p~~iton I

115

I

792

I

268

I

151

-

17(11.2)

The germination was not good, but all seedlings looked healthy and grewwell. Chromosome counts were not undertaken, because the plants giveroots only once a year.

•
5. Genetics of Flower Characters in Zinnia e/egans(Report by Kanji GOTOH)

In 1951, crossing between single and complete double as well as between
non-petalous and many other types were undertaken. Selting of F 1 hybrids was also made. The flower of F 1 hybrids between single and complete double flowers showed the following structures :-the basal part of
the flower was constituted of 1-2 layers of florets with petals, while thetubular flowers occupied the remaining part except for the top having38

some petalous florets. This type has been identified with "E type"which was realized in the writer's experiments conducted in 1950. Experiments are being continued.

6. Sterility in Phaseolus multijlorus(Report by Akira MIYAZAWA)•

P haseolus multijlorus is known to be fully fertile in its natural habitat
which is in cool mountainous districts like Nagano or Hakone. The planttransplanted from Hakone to the experimental garden in the instituteexhibited high sterility. On September 2nd 1950, about 20% of pollen
grains were found to be empty. Moreover, the ratio of empty pollen
grains declined with the progress of the season. It was assumed thatthe high temperature of the very hot summer in Misima is the cause ofthis sterility.
The present report deals with observations of the meiotic behavior ofthis plant. In the maturation divisions ofP.M.C. 's, various irregularities
were frequently observed. At the first metaphase one or more univalentchromosomes were seen outside of the plate. Some chromosome bridges
were found at the first anaphase, and some lagging chromosomes wereobserved at interphase. The polar views of the second metaphase showed
10-12 chromosomes in the nuclear plates, while the expected normal number
should have been eleven in each plate (2n=22). In the tetrad stage thenumber of microspores was mostly four, but a few mother cells contained two, three or more than four. The size of the pollen grains wasvery variable. It seems that the E.M.C.'s behaved in a similar manner.
The phenomena described above seem to be analogous to the observations made in plants treated with high temperatures. These cytological findings support the author's previous hypothesis. However, thevery high degree of sterility does not have a fully adequate counterpart in the meiotic behavior. Therefore, ecological factors should also
be taken in consideration. This will be the subject of the investigationsof this year.
7;

Paper Chromatographic Studies of Flower Color Variation(Report by Toru ENDO)

The writer has made some introductory studies on chemico-genetics offlower color variation by paper chromatography, using six Dahlia varieties in 1951.
1% methanolic hydrochloric acid extracts of fresh petals were chromatographed on T6y6 filter paper No. 2 with n-butanol acetic acid:water (4010-50 volume %). The results of this experiment are as follows: .

39

Table 1-Anthocyanin

Flower color
white
mauve
pink
vermilion
purpledark red

CyaninPelargonin(0.25 ± .06) (0.34 ± .04)

Flavonoid
Yellow
Bro~n(0.39 ± .09) (0.49 ± .06)

++
+

+
+

++
+
+tt

ill

+It

.I

+

+

++

++

+
+

ill

+

ill

++

+

ill

Numbers in brackets stand for the R f values and+, or ill indicates the relative quantity of the pigments, - indicating none, ill the
maximum quantity contained.
As is illustrated in this tab~e, there has been found a remarkable parallelism between the intensity of .flower color tones and the amount of
the component pigments. It was also found in this experiment t4at thepelargonin was always accompanied by fluorescent substances (light yellow fluorescence).
Similar experiments are now in progress with Viola tricolor, Verbena
hybrida, Impatiens Balsamina, Antirrhinum majus and Petunia hybrida.

J.

IMPROVEMENT OF SOME USEFUL PLANTS

1. ImprQVement of Sugar Beets by Means of Induced Trip/oidy(Report by Seiji MATSUMURA)

Triploid beets are more vigorous, grow better and always show a higher
yield, a higher sugar content and a higher resistance to diseases than the
diploid Hon-iku No. 192, the most widely grown variety, according tocomparative studies carried out on a large scale in various districts of
Hokkaido. The triploid seeds, however, are inferior in germination rate.
In order to solve this problem, various intervarietal triploid hybrids wereobtained and compared with one another.
.
The germination rate of the tetraploid seeds is variable; it is very low
in Hon-iku No. 48-4x, but relatively high in Hon-iku No. 398-4x and No.
402-4x. Therefore, the triploid combinations No. 398-4x X No. 162-2x and
No. 402-4xxNo. 399-2x are most promising.
For the large scale production of triploid seeds it was found advisable
to plant 4x and 2x beets in the ratio of 3: 1. In this way relatively many
triploid plants were obtained.

40•

2. Genetics and Breeding of Citrus(Report by Kazuo FURUSATO)

•

'f

-.

A. Pathenocarpy and' seed reproduction
Citrus Unshu has usually no seeds in the parthenocarpic fruits. Thisis due to pollen abortion which takes place in our climate in the earlyand middle parts of the flowering period of this variety. Therefore, evenartificial self-pollination fails to produce seeds. However, when pollinatedwith good pollen of another variety (e. g. Citrus natudaidai orC.
tamurana), C. Unshu easily sets .seeds. This indicates that C. Unshu. can produce normal seeds, provided that good pollen is available.
Infact, normal seeds of this variety can be easily obtained later in season,
when its own pollen is well developed. The failure to yield good pollen
is apparently due to the influence of the high' temperature prev<,liling
during mpst of the flowering period in our country.
Parthenocarpy without pollination occurs in C. Unshu. Even when thepistils are cut off before the opening of the flowers, the same amountof fruits will be set as in natural condition.
.B. Polyembryony
Studies on polyembryony in Citrus have shown that many additional
embryos are formed from nucellar cells after the fertilization of the egg
cell. The number of embryos per seed varies from species to species,and even among the seeds of the same variety.
In Citrus Unshu 20-30 large and small emb:t;~os were counted in one
seed. This number is higher than that hitherto reported by other authors. This difference is due to different methods used in counting the
eplbryos. The embryos vary in size (rom very small to normal. 1'heuse of a microscope for counting will increase the number of embrY9s
counted. The number of plants which. developed was considerably. lessthan that of the embryos.
When the seeds of C. daidai are sown in the soil, only 1-4 embryos
develop into plants against 16 embryos on the average develop from OJ~eseed. When the embryo-culture method is used, seeds sown on agarshow a better development of the embryos than when planted in thesoil. However, not all of the embryos are able to develop.
As to the relation between polyembryony and the ~ature of the pollen
parent, when polyembryonic varieties are pollinated ~ith pollen of monoembryonic varieties, all seeds produced are polyembryonic, but when thereciprocal pollination is carried out, monoembryonic seeds are produced.
Thus, the nature of the pollinator has no influence on the number' ofembryos prOduced. Further experiments will show whether some kind.of maternaIinheritance or influence has to be taken into considerationin this case.
41

3. Induced PolyPloidy in some Cultivated Plants and its Utilization(Report by Kazuo FURUSATO)

A. PolyPloid watermelons (Citrullus vulgaris)
In order to breed new varieties of triploid watermelons, three newly
induced tetraploids of the varieties 1. K. (provisional designation) andKanro were obtained. These new tetraploids were alm.ost'of the same
type in morphological and ecological features as those obtained before.
Tetraploid Kanro attracted my attention on account of the very vigorous
growth of its vine. So I planted it mixed with some diploid varieties
such as Yamato, Asahi, Miyako and others, hoping that new triploids
might be produced by cross pollination. These triploids, if found, will
be selected on the basis of yield, quality of flesh and disease resistance.

B. Grafting stocks for triPloid watermelons
Triploid watermelons were grafted last year on di-, tri- and tetraploids and on calabash.. In plants thus obtained the quality of fruit flesh
and the development of empty seeds were examined. Grafting was triedalso on other species, such as Cucumis sativus artd Cucurbita moschata.
When Cucurbz'ta was used as the stock, many fruits were produced, butthey contained many empty seeds. When cucumber was used as thestock, the yield was low, but the number of empty seeds was small.
,C. TetraPloid melon (Cucumis Melo)A tetraploid plant was obtained by colchicine treatment from Nara No.
1, one of our melon varieties. The fruits of this plant were flat, andhad a thick flesh layer. Their appearance was not attractive, becauseof an overdeveloped hilum, but the thickness of the flesh and the deepcoloring of· the skin are desirable characters. Further attempts will bemade to obtain a good tetraploid variety of melon.
D. TetraPloid racf! of Medicago denticulata
A tetraploid race obtairied from Medicago denticulata had longer andthicker stems than the diploid race, but their number was smaller. The
yield will be investigated in the field.

K. STUDIES ON SOME LOWER ORGANISMS
1. Effect of X-ray Irradiatz'on on Streptomyces griseus(Report by Seiji MATSUMURA and Taro ITa)

The present study was undertaken in cooperation with the Fuji Plant,
Ky6wa Hakko Co., in order to obtain by irradiation with X-rays'a high·potency mutant of StrePtomyces griseus, which is being used for the production of antibiotics.

I•The spore suspension, prepared in variou,s concentrations (1.5x 10~/cc,
1.5 x lO s/cc, 2.5x 106/c.c), was exposed to X-irradiation, operated at 180 KVP,
3 rnA, without filter. The doses ranged from 5,000 to 150,000 r units.
The logarithmic curve of survival ratio to dosage, appearing more orless linear at any concentration, confirmed that the organism was killedby the direct effect of one hit of X-rays.
Morphological mutations induced by the irradiation appeared as f. inst.
yeast-like and grey-colored strains which were low-yielding. The irradiatedcultures showed, in general, a very wide variation in the yield of theantibiotic substance, and at low X-ray dosage a variant was found which
was 10 to 20% more potent than the untreated strain.
The stability in the yield of streptomycin was investigated by subculturing (from the view point of mass production). By subculturing a greycolored type was found to revert gradually to the. normal white.
These results give hope for the production of a high-yielding strain by
X-ray treatments.

2. On a Heterokaryon in Aspergillus candidus(Report by Seize) TSUDA)

In many species of Aspergillaceae, development of the perthecium
occurs very rarely in nature, and multiplication of the fungus is usually
through the production of conidia. Though these fungi do not form
hybrids, a phenomenon analogous to hybridization has been found tooccur. In this process, one or more nuclei migrate from one ceil intoanother, and produce a heterokaryon. This phenomenon has been studied
by SMITH and HANSEN (1932) on Mucor, and more recently by BAKER(1944) on Penicillium, by PONTECORVO (1946) and by SAKAGUCHI and ISHITANI (1951) on AsPergillus, among others.
The writer found in the fall of 1951 a case of heterol;<aryosis in astrain of Aspergillus candidus. From the culture of this heterokarYotic
cell a morphologically different strain was segregated. This new strain
was cultured repeatedly as many as ten times, and found to retain its
morphological characteristic, no further segregation occurring. Accordingly, it was assumed that this strain had become a homokaryotic strain.
In this newly segregated homokaryotic strain, the conidiophore was foundt6 be relatively shorter, and the size of the conidiospore was somewhat
small~r than in the heterokaryotic strain. The conidiophore was coloredwhite, and the shape of the colonies was round.
It has been noticed that the heterokaryotic strain has a· lamella., ~c;lthe homokaryotic strain a hexenring. The culture media u,sed was ~alli;".;5° wort aga.r, and cultivation was carried out at 28-29°C.

43fhese sporeS were stained with ROBINOWIS Ciemsa method (1941)affet
fixation and hydrolyzation by normal HCI at 60°C for 7 minutes. ObserVation of the preparations has revealed that the spores of the heterokaryotic
strain contain many nuclei, from five to twenty in each, while the sporeof the homokaryotic strain usually contains only two or three nuclei.
Cytological and enzymatic studies on these strains are now in progress;

3. Studies on Neurospora crassa(Report by Taro ITO)

A. Rate of production of fruit-body in different culture filtrates
Experiments have been conducted to study the mode of fruit-bodyformation in the filtrate of the culture of one of the mating types 4A,
and Sa, and in the filtrate of the mixture of these two types. The filtrate
was prepared by passing a 72 hr. culture through a Seitz filter into an
Erlenmeyer flask. WESTERGARRD and MITCHELL'S culture medium wasadded to this filtrate before inoculation.
Many more fruit bodies were formed in the culture medium containing
the filtrate than in the control without the filtrate. The fruit-body formation was especially profuse in the culture medium to which the mixed
culture filtrate had been added.
From the above result, it may be assumed that some substance or'substances which promote conjugation and fruit-body formation are pro':'duced. The relative power of the three kinds of filtrates in producing
this effect is in the order of (4A+Sa»4A>Sa.

B. Growth Promotion of culture medium filtrates of two mating types·
In order to study the differences in physiological activities between thetwo mating types, 4A and Sa of N. crassa, the growth response of theSe:
types to the filtrates of their cultures was examined on the basis of thefollowing presumptions :(1) There is no difference in promotion activity between the homotype;
and the heterotype; that is, the culture filtrate of either the 4Aot Sa'
shows equal effect on the growth of either type.
(2) There are some differences in promotion activity between 4A and
Sa, thus:. a. The culture filtrate promotes the growth of its own strain.
b. Each culture filtrate promotes the growth of the other strain, .thatis, the filtrate of 4A promotes the growth of Sa and vice versa.
In the investigation, the rate of growth response induced by the filtrates
was measured by weighing mycelia growth on each filtrate by the methOd
described in the writer's previous report, and the results were analyzed
by the variance analysis method.

••

It·· has been found that the 4A strain responds more vigorously to the Sa
culture filtrate than the 8a strain to its own filtrate, while both strains
hardly showed any differential growth response to the 4a culture filtrate.
4. Studies on the Virus Infecting the Silkworm(Report by Mitsuo TSUJITA)•

A. On a metkod of ProPagation of the virus infecting the silkworm
It is well known that the so-called polyhedral bodies contain infective
virus, and that the caterpillars can be infected by eating mulberry leaves
contaminated with the polyhedra. There is, however, another important
method of propagation of this polyhedral disease. It consists in thetransmission of the virus in a latent condition from generation to generation. This has been ascertained by the facts described in the following.
Several egg batches ofa silkworm strain highly susceptible to the virus
were< used in this experiment. Each of the batches was divided into twoparts, and one of them was treated with diluted hydrochloric acid abOut
20 hours after oviposition. A special room was used for the incubationof .the egg material and rearing of the larvae. The temperature andhumidity in the room were variable, according to outdoor conditions insummer. The other half of each batch was placed first in a room at
25°C for 40 hours after oviposition, and then it was refrigerated for 60days, or kept in a resting condition at room temperature. The eggs
were incubated and reared in a thermostat at 25°C and 75 to 85% humidity.
Of the two lots mentioned above, the former produced jaundice-diseased
larvae on the second day, and in some lots all of the young larvae diedbefo.re the first moulting, or by the end of the second instar. On examination of the young larvae which died within twenty hours after
emergence, a large number of polyhedral bodies were found, whereas in
the latter lot only a small number of larvae died of the disease, andalmost all· of the apparently healthy larvae developed through pupal
stages. to emergence. It is scarcely possible that so many polyhedralbodies- could have been produced within twenty hours after hatching if
infection had entered from the outside of the eggs at the time of emergence of the larvae. This observation seems important because it indicatesthat the virus must have resided in the developing embryo, instead ofcoming from outside the shell. It is out of question that the virus had beentransmitted from the female parent through the ooplasm, and multipliedin the functional cell in a later embryonic stage.
In short, whether the polyhedra are formed by multiplication andgrowth I:Jf the virus in tissue cells of the larval body or· not, there is no
doubt that this is controlled by environmental factors in the larval stage.
This is also apparently true even for the pupal stage. This also suggests,
45

that the· virus in the latent state is activated by envitonmental stimuli,
and muliplies and grows, causing the disease.
Thus, the polyhedral viruses must be .capable of lying latent withinthe· silkworm through all its developmental stages. Such a virus isgenerally called by the name of "latent virus". The phenomenon thatthe pathogenic agents in the latent state are transmitted from parent tooffspring, and the polyhedral disease develops through stimulation byenvironmental factors, should be distinguished from real. cytoplasmic inheritance. Therefore, it is proposed to call this phenomenon "pseudocytoplasmic inheritance ".
It has been shown by L'HERITIER (1948) that sensitivity to CO2 in
DrosoPhila is controlled by a kind of cytoplasmic unit called by him" genoid" or "sigma", This body is transmitted from parent to offspring through the ooplasm and possibly by the sperm also. However, it
has, in the meantime, become fairly clear that this cytoplasmic unit isa symbiotic or parasitic virus, because it is contagious. The silkworm
virus under discussion bears similarity to this genoid in many points.
ISHIMORI (1940) and YAMAFUJI (1949) claim that the virus in the silkworm
can be artificially produced de novo by physical and chemical stimulus.
Indeed, when the silkworm is refrigerated or injected or fed with various
chemicals such as hydroxylamine, potassium nitrite or hydrogen peroxide,
it often develops a polyhedral disease. Such an observation might tempt
one to a belief in the spontaneous origin of this disease. However, since
this virus is apparently transmitted from parent to offspring throughooplasm much as is sigma in DrosophUa, it is more pausible that thevirus is already present in the animal in a .latent or dormant state, andthat a physical or a chemical treatment may activate it to multiply andgrow, and to start the disease.
B. On the multiPlication and growth of virus in living cells
The virus particles which appear in the blood of the silkworm in earlystages of jaundice disease are from 10 to 30 m/.l in diameter. These seemto be virus units liberated from the tissue cells in which they have multiplied. The units multiply by duplication and development, and become
Rickettsia", or DiPlococcus-like granules 400--450 mp in length and 100-150 mJ.l
in width. Each of. these granules contains one to several mature thinrod-shaped virus particles, each of which in turn consists of a number ofunits. The large part of the protein composing the polyhedra is producedin the course of reproduction and growth, probably by some activity ofthe virus. Consequently, various developmental stages of the virus are~ntained in. each polyhedron. In some cases, rod-shaped particles andspherical particles about 50-100.mpin diameter can be recognized in thepolY1J.£ldnt. . WYCKOFF and SMITH (1951) observed similar virus particles
ij.~~~ fr.Qmpolyhedr;iwhich had developed in the larva of the garden
46·

•

..

tiger moth (Arctiacaja), by dissolving them in dilute alkaline solutiort.
They state that at least two different kinds of this disease may be foundin certain Lepidoptera. As reported by BERGOLD (1950) and TSUJITA (1951),
the silkworm virus has a kind of life cycle within the host cells. It
seems that some primitive phase of this life cycle is transmitted as alatent virus or provirus to the next generation through the ooplasm.

L. THEORETICAL GENETICS•

1. EICPerimental Demonstration of the Theory of Variance

Increase due to Competition in Plant PoPulations(Report by Kan-Ichi SAKAI)In the 1951 issue of the report of this Institute, the writer advanced atheory postulating an increase of variance caused by competition between
plants of different pheno- or genotypes in a heterogeneous plant population. The present report describes the results of an experiment withartificially mixed wheat. populations undertaken for the purpose of demonstrating the theory.
Plants of three varieties of wheat, called A, Band C for convenience's
sake, were individually space-planted in rows in four different mixtures;the three varieties were also planted without mixing. The experiment
was conducted according to the complete randomized block design withfour replications. Young seedlings were transplanted into the experimental
field in the fall of 1950 so that plants of the varieties to be mixed wereplaced at random. Data were taken on the basis of the dry plant weight
and the number of heads on plant.
(a) Effect of mixing varieties on plant characters.
According to the result of variance analysis, it was found that theplant weight as well as the number of heads of a given variety weresignificantly affected by the coexistence of another variety or varieties.
It has been found that, with regard to competitive ability, A~B>C.
(b) Estimation of increments due to competition.
In order to make such estimations, it is necessary to introduce thefollowing premises for the uncertain or unknown part of the experiment ;-(1) Competition occurs only between neighbors in the same row.
(2) Increments in one plant due to two neighbors accumulate additively.
Estimation was made by the method of the least squares, with the resultthat all of the increments effected by competition in mixed populations,
except in the A +B population, were significantly different from zero.
(c) Increase of variance due to interplant competition in mixed populations;
Taking three adjoining rows at random so that we may have approt-47

imately a one-hundred plant population from each plot, .variances w~te
calculated and the variance of variances was analyzed. It was shown
that, with regard to plant weight, the amount of variance in mixed andnon-mixed populations differed significantly at the 5 percent level of probability. As the mixed plant population contains plants of different genotypes, the variance of any character in the population should naturally
consist of three components; i. e. the environmental, the genotypical andthe competitional. The question is: whether any variance due to competition actually exists in the mixed populations of the present experiment.
In order to answer this question, the following analysis was made.
(d) Determination of variance due to interplant competition.
In order to determine any variance which would be attributable to theeffect of interplant competition, comparison was made between the varianceof the mixed population and the variance of an artificial population
constructed from two or three groupS of data obtained from non-mixed
populations.
Differences between the corresponding two variances represent thevariance due to competition between plants of different genotypes; that·is, the variance due to competition and interaction between competition
and the genotype. Analysis of variance made on this set of variance differences showed that the variance due to competition (including thecompetition-genotype interaction) differed highly signficantly according to
the varieties mixed.
The extent of increase of variance is different according to the combinationof varieties, being approximately zero in the A + B population, fairly large
in A+B+C and B+C populations and very large in the C+A population.
With regard to the number of heads per plant, no significant increaseof variance in mixed populations was observed, although there was ageneral tendency of increase of variance, approximately parallel to thatconcerning plant weight.
Thus the writer's theory of variance increase due to interplant competition in plant populations has been demonstrated to be valid by theexperimental data. This suggests the necessity of a correction in themethods of biometrical investigations of some plant characters. Furthermore, the present theory presents interesting problems concerning plant
evolution as well as plant breeding.

2. Competition Studies with Six Varieties of Rice
(Report by Kan-Ichi SAKAI)

Competitive ability has been studied in six varieties of rice-plant. The
number of experimental plots in one block was thirty-six, covering all
combinations between any two of the six varieties.. 25 cm2 space-planting
48

•

•

otJndiVidua1t>1antswa8 made according to the6x6 'simpleJatticedeslgn
with four 'repliCations~ After harvesting, dry-plant weight, plant' height~
total weight of panic1e~, number. of culms and panicles and length of ,thefiistpanicle' were determined on a plant •basis.
By the analysis of varian<;e, all of the characters studied showecLhighly ,significant differences among the varieties, separately grown or mixplanted. Average increments of characters of each variety surrounded by
the other five varieties were calcWated,and'analysis, Of variance wasagain pursued to find whiCh would be ,more effective in the role of thesurrounding or the surrou11.d~d ,v:ari~ty. As indicated in Table 1, thisanalysis has disclosed that the differences in increments due to competition
tend to show higher significance in eaQh variety when it behaved as'asurrounded plant than as aSllrroundingplant.
"Table 1. Analysis. of variance of ingrementsof charactersof varieties, due tointervarietal competition
d.f.

Plant
weightPlantheightNumberofculms

Numberofpanicles'Weight Lengthofof 'panicles, panicle

Variety as a6
surrounder
Variety asa
surrounded one 5
Error
25
l·:~

76.6**,:,,:.'....

3.7

1.8*

-1.4*

12.1

O.~

112.9**
"

6.9*

4.4**

2.1**

67.7**

0.56

0.6

0.4

4.9

0.23

Factors

,j

...

2.6
__lfj.3._------_..

_------~.'------------,---* Exceeds the 5 percent point.

** Exceeds the 1 percent point.

A, comparison of thecoI11petitive ability of various varieties

when,sur,Here the stanclard
errdr ofthe average.jncren:1-ents of the varieties surrounded by five othervarieties is taken as·a unit~
rouadedby,oth~rvarietie§is illustrated in Table 2.

Table 2. Distribution of six varieties of rice on the basis ofcompetitive
abiiity. Unit of scale: Standard error
"t',
~'.

CharacterSt
I -Qistrlbution of, six varieties measured by the, competitived':d"increments on a standard error seale
arror 1-6.61-'5.6\-4.51-3.51-2.51-1.51-0.51 +0.5h1.51+2.5!+3.5

Total weight
Plant height

1.661
1
I A
-----1-,0.64 Iil'
I,'TIS I N'1'2.,'

1--1-\- KI',-~------,,KSA
N" ,.,T\ ' '
'
" ,

'1';-

Number of
SK T,N
culms 0.30 ! A ! - ' - - - .
0 . 2 5 , - - ! A - - - - - - - - ' '1'11'2 KSN
Number ofpaniclesWeight ofNTipanicleso.90f/A--\--I--,-'-.'--s-:
49,

'1'2

,-----~)" [KT2 -The 'average competitive ability of N, S, and T 1 are shown to be a~
proximately zero, while the capacity of A, .T 2 and K has a. plus orminus value for more than one character. It is especially noticeable. thatthe competitive ability of A, the only glutinous variety, Called ASahi.mocW,
for all characters except plant height shows negative value.

3. Theoretical Studies on Selection in the Breedingof Autogamous Plants(Report by Kan.lchi SAKAI)(1) Selection of quantitative characters.
Quantitative characters in plants are often supposed to be controlled bya number of multiple genes, which have similar and additive effects.
Though it is in many cases very difficult or even impossible to analyze
the genotypical constitution of such characters on account of considerable
fluctuation, they often provide good material for successful selection work.
The present paper deals with a theoretical consideration concerning theeffect of partial selection on quantitative characters in a hybrid populationof autogamous plants.
Assumptions are made that the pairs of genes concerned are two. i e.
Xx and Yy, assorting independently of each other, and having the sameand additive effects. The sel~tion, accordingly, deals only with plu~~genes.
Frequencies and selective values of genotypes involving four to zeroplus~genes are given as follows:
Number of plus-genes
4
3
2
.1
0 .
Gendtypes and their relative XXYY XXYy(b) XxYy XXyy(d) xxYy(g) xxyy
frequencies in parentheses: (a)Xx YY(c) (e)xx YY(f) Xxyy(h) (i)Selective valus of genotypes:
81
82
83
83'
84
86

Frequencies of any genotype in the nth generation can be computedfrom the formulae given below:

•

1

.

11

1).1

/,,= ( S"/"-1 +S'4:"-1+ss4 . ~"-1 +S44 gn-l I W n-lg,,=(S4 ~g"-1 +Ss ~; i!"-I)!Wn-1

hn=(S4 ~ h n- 1+Ss ~ . ~ en-I)

jw n-li n= (S6i"-1 +Ss 1~ e n-l +S4 ~ gn-l +S4 ~ h"-I) / W ,,-1·..

Here W"-1 stands for the mean selective value in the (n-l)th generation
which is formulated as,
W,n-l=s~an-l+S,(bn-l +Cn-l)+sSe n-l +ss,(dn-1+/n-l)+S4(gn-l +hn-1)+S6in- 1.
Since the, selection is repeated' during each of the successive generations,the total number of individuals in the nth generation is proportional toWn, which will be expressed a~:"-1

Wn=WoW 1W, .... W n-l= II WJ
J-O

(n~l,

Wo= 1).

Let Wnan, wnb n, .... , wni n be An, B n, ..•. , In, and the selective
..
S,
Ss
S4
values be represented as sl=K1, 2=K" 4=Ks, ss,=Ks', 2=K4 ands6=K6, the following equations result:

J

K 2K s ) [ L(1, 2)-L(1, 3) +4L(1,Kd
A n= 2(K,-K3),
s1

Bn=Cn=2KsL(2, 3),
En=(Ks)n,n
D =F =K {K,[L(3' 2)- (4 -l)Ks"-I]n"S
4(K,-Ks)'
3n1
4 - K sn-l (1)
K4 ['(4n-1)Ksn-l]}+
3
1- 4n + 4(K 4-Ks) L(3, 2)3.
Gn=Hn= ~KsL(4, 3),

J.

4
4

K -Ks)
Ks [ L(5, 4)-L(5, 3) +4KsL(5,1I n= 2(K3) ,where L(i, j) stands for

Kln-KJn
K K .
1-

J

Assuming the selective value of any genotype with a given number,ofplus-genes to be lor 0.1, the proportion of'XXYY plants in some hybrid
generations is presented in the following Table 3.

51

Table 3
Genotype

No. of pIns
genes

XXYY
XXyy, Xxyy
Xxyy
XXyy, xxyy
Xxyy, xxyy
xxyy

4
3
2
2
1
0

PropOrtion of
XXYY
in percent

F,
F6
Fe

Selective values
1
1
1
1
1
1

1
1
1
1
1
0.1

1
1
1
1
0.1
0.1

1
1
1
0.1
0.1
0.1

1
1

O.f
0.1
\' 0.1
0.1

1
0.1
0.1
0.1
0.1
0.1
.,

19.14 22.06 30.57 46.43 75.39 89.70
23.46 29.93 39.48 81.86 93.38 99.93.·24.90 33.15 42.05 98.77 99.61100.00

It is notiCeable from this table that the proportion of XXYY in later
generations will be considerably affected according to whether the selection of XX", and xx YY be possible or not.
(2) Effect of a single mass-selection during segregating generations ofa hybrid population of qutogamous plants.
In a single mass-selection conducted in one of the segregating generations. of autogamous hybrid plants, the degree of efficacy of the selection
for Securing as many homozygous dominants as possible should be computed by taking into consideration the time of occurrence of the selection.
A brief consideration will be here given.
Let the numbers of segregating generations before and after any single
selection be n and m respectively, and the total number of segregating
generations N( =n+m), and also, let the selection coefficient of recessive
genotypes be 5, then the frequency of phenotypic dominants in the Nthgeneration, DN, may be computed by the following formula,1

1

JT =t~
1
1+ 1 )T 'DN=t[ 2+~r (2Nwhere t is a function of 5 as given below and r stands for the numberof corresponding gene pairs.
1

The following table illustrates the percentage of phenotypic dominantsin F 7 in a hybrid population which has been subjected to ~ single selection, faking all dominants and ten percent of all recessives· in any of theF 2 to F 8 generations.
52...

Table 4
Number ofgene pairs

Without any
selection

1
3
6
10
16

60.78
13.30
3.38
0.11
0.004

With a single mass-selection in
F4
F6
Fa
66.62
76.66
83.76
87.84
27.30
40.96
60.33
66.74
10.77
18.17
22.41
24.46
0.76
1.06
1.11
1.12
0.03
0.04
0.04
0.04
F2

Fa:
90.03
68.62
26.43
1.13
0.04

This shows that a single selection during cultivation ot a hybrid bulk
is effective in increasing the number of desirable dominant genotypes in
the final population, and that the later the selection occurs, the greater
the chances of the success.

4. Fluctuations of Adaptive Values and the Frequency Distributionof Heterotic Genes in Natural PoPulations(Report by Mota KIMURA)•

A. Long term distribution determined by random fluctuation
It is well known that in panmictic populations the superiority in adaptability of heterozygotes over their corresponding homozygotes willlead to the maintenance of more than two alleles or chromosome types
in stable equilibrium (d. WRIGHT 1949; BRIEGER 1950, etc.). Recent experiments on natural populations have revealed that adaptive values of many
genotypes undergo both random and cyclic fuctuations, which are often
characteristic of the coadaptation mechanism, that· is, the mechanism ofmutu"aladjustment of the gene contents of different chromosome types(d. DOBZHANSKY 1950, 1951; FISHER and FORD 1947, 1950, etc.). The
following is a result of mathematical investigations on these problems.
Let :I: be the relative frequency of a gene (or a chromosome type) A,
and let 1-:1: be that of its allele (or a different chromosome type) A' ina panmictic and sufficiently large population. If the adaptive values of
the three genotypes AA, AA' and A'A' are respectively 1-s, land 1-i,
and the mutation rates of A to and from A' are respectively
and v,
then the mean (Maz) and the variance (Vb) of the rate (ox) of changeof the frequency of A per generation amount touandMaz= -s:l:2(1-:l:)+t:l:(1-:l:)'-u:l:+v(1~:I:)

Vaz=:I:'(1-x)2{Vs:l:2-2Wat:l:(1-:l:)+ Vt(l-:l:)'},
where S. t and Va, V t respectively denote the means and variances of
selection coeffl,cients,i.e. sand t, while Wat is a covariance between them.
Under these conditions, the probability density q>(~,x) for the frequency

of A in the 't"-th generation satisfies the following FOKKER-PLANCK
equation (ct. WRIGHT 1945):
fhp('t",:t;)
a't"

(1)

1 a'

a

2 a:t;'[Vsz~('t",x)]- ax [MSz~('t",:t;)J.

Assuming that the means, the variances and the covariance of theselection coefficients are all constant fora long period and W,,'- V, V,<O,
then the solution; ~(x), for the stationary state; a~('t",:t;)la't"=O, becomes(2)- 2 {-8+ 3V, +2W., U-'lI- V , }~(:t;)=C{(x-a)'+I1'}-.d-l(I-:t;)V ,V,

X:t; :, {t_u+_2~~3V''lI_V,}

I

xexp {_2Btan-l(:t;-a)_~(_1)-~(.!.)},
11
V, 1-:t;V,:t;S + t + V,V,+t -(V, - V,)' u + V,V,+t -(V, - V,)' v

where A =V,

V,

V,, V,

B VV'V,I_ Wit' {(
+

V,V,,

'

1+ ~:' )5-( 1+ ~:')t(W,,+ V,) V, V,+,-2(V, V,- WIt')(V,- V,)V,'~u(V,+ W,,) V, V,+t+2(V,V,- W,,')(V,- V,)

V,2V,
a=(WIt + V,)IV,+, ,}V,

l1=vV, V,- W,t'/VS+, ,V,+,= V,+2W,,+ V,

and tan-IX takes a principal value.

t~(:t;)d:t;=

The value of C is chosen such that

1. From the "ergodicity of stationary stochastic process", theformula (2) gives the long term distribution of gene frequencies in natural
populations. Since u and v are usually expected to be much smaller than sand t, the distribution curves centre around -the equilibrium frequency;
i:=tj(s+t), as V, and V, tend to 0. So in this case the ratio sIt is thedetermining factor for the frequency distribution. But if V, and V, are
not negligible for s and t, the ratios slV" tlV, and the correlation
coefficient ('Tit) between s and t, as well as S;t~ are all important for the
distribution.
For cases of coadaptation, the values of r" may be expected to beapproximately -1. The estimation of the above mentioned parametersin natural populations would be an important task left for future experi~ents.

54•

B.· Process of the change of gene frequencies due to the cyclic andrandom fluctuations of selective values.
As the simplest model of coadaptation, let us consider the case in which
one. cycle consists of m generations and S=CI sin (2n-rlm), 1= -C 2 sin (271.-rlm),
where CI:2:C2>0. To make the calculations simpler, let us assume further
that there is a complete negative correlation between sand t (r.t= -1),
that their coefficients of variation are equal in absolute value (11 v./1 s I =VVt! Ill), and that the change due to mutations is negligible.
Putting 11 V.lCI = VVt/c2~k( -r), the mean and the variance of ox become
respectively

andVo x =x2(I-x)2{c2+(cl-c2)x}2k'(-r) .
If the frequency x is transformed into z either by the relation:z=-llogc(_X_)(if CI=C2=C)

I-x

or by the relation:11. ) CI-C2

C2

CI

CIC2

z=·--logx--~ log (l-x - - - - . log(.. C2··-.
CI -C2--+ x )

of Cl

(1

> )
C2

,

the resulting variate z may be regarded as a scale for the gene frequency,changing continuously from - 00 to + 00 as x changes continuously from

°

to l.
Under this scale, the mean and the variance of the rate of change pel"generation become simpler, being
Mo z = -sin (~-r)

andVs.=k 2 (-r)

approximately.

So if the number of generations (m) in one cycle is large, the.probability
density if>C-r,z) in the -r·th generation satisfies the equation:~_k2(-rt82if>+sin(~-r)~

(1)

,

8-r -

2

8z 2

m

8z'

which represents a spatially homogeneous MARKOV process.
The solution of this equation isif>(-r,z) =1
V2n:0 7exp[[z -~cos(~-r)+~-zoJ'}
2n:
":
2n:
,(-r>0) ,207

where 0 2= ~:k2(-r')d-r' and zo is the value of z at the start (-r=0).
7

every cycle, the mean value of z;
z=zo+ ;: {cos ( :55-r ) -

I}In

returns to its original value, Zo, while the variance increases by (1.,,2=~~k2(~')d~'. In a sufficiently large number of generations, the increase invariance will be counterbalanced by mutation or migration, and theprobability distribution for a given generation would become independentof the inital condition (zo), though I have not succeeded in obtaining theformula for that distribution.
From the comparison of the series of values between z and S, it may
be clear that there is a shift by m/4 generations between the periods oftheir maxima and also between their minima, so that the period atwhich the frequency of AA becomes maximum or minimum lags respectively by m/4 generations behind that at which its adaptability becomesmaximum or minimum. This indicates that, against the cyclic change inthe environmental conditions, the mode of adaptation due to the "coadaptation'~ mechanism is less effiicent than that due to the direct change ofphenotypes.

5. Process of Irregular Change of Gene Frequencies due tothe Random Fluctuation of Selection Intensities(Report by Mota KIMURA)

In the mathematical treatment of the process of change by selection, it
has commonly been assumed that the selection intensity is constantthroughout many generations, though in practice the intensity must be
subject to fluctuations. In the present investigation random fluctuationof the selection intensities is assumed to occur and the resulting MARKOV
process is investigated.
Let x and I-x be respectively the frequencies of a gene a and its allele
A in a population which is assumed to be very large and panmictic. The
rate of change of frequency of a per generation, if there is no dominance,is8x=sx(l-x) ,while it is
8x=sx2 (I-x) ,if A is completely dominant over a. Here s stands for the selection
coefficient of the gene a in the former case, while it stands for that of
the recessive individual (aa) in the latter case.
If the frequency II: is transformed into the variate z either by
Z=log(_X_)
I-x(for the case of no dominance)

or by

56

z=

--.1+10g(~)(for the case of complete dominance),x
I-x

the rate of change of the value of z per generation becomes
(Jz=s

,

in either case. If the gene frequency in the population is measured bythis z scale, it changes continuously from - 00 to + 00 as x changes fromo to 1. The mean and the variance of (Jz are equal respectively to themean (5) and the variance (V.) of the selection coefficient (s).
-Thus, under the z scale, the process of the change of the genefrequency can be represented by a temporally and spatially homogeneous
MARKOV process, the transition probability of which is_(Z~8t-ZO)2

1

, /
V

2nrV.

e

(T>O) ,

2V.t"

and hence often called "GAUSS process" by mathematicians.
Therefore, if xo is the initial gene frequency (T=O), the probability;(P'T(x)dx that Xo changes into x-x+dx through the selection extending T
generations, is:_)2)x(1-xo)( log x n ( l-sr
- x ) _ d~ _

2V.T

I

xCI-x) ,for the case of no dominance and1rn'T(x)dx =
T

•

.

. exp

V2nTV.

_(lOg x(1-xo)
xo(l-x)(~_~)_Sr)2) d

2V.T

x

xo

.

x
( >0)
x 2 (I-x) , T,

for the case of complete dominance.
This process should proceed indefinitely, if there were no disturbanceby gene mutation, though in practice the advance will finally be checkedby the opposed mutation pressure.
In the above discussion, it has been assumed that sand V. are constant.
If they change from generation to generation, they must be treated asfunctions of T, so that ST and V.T in the above formulae must be replaced
respectively' by 1:S(T')dT' and ~: V.(T')dT'.

6.

On" Effectz"ve Size of PoPulations"(Report by Mota KIMURA)

The concept of "effective size of population", which was introduced bypapers, is fundaIJlental in dis-

WRIGHT (1931) and developed in his later57

cussing the frequency distribution of genes in natural populations.
Recently, the present writer attempted a mathematical study on thisproblem, and some of the results obtained are reported here.
Let us consider a sexually reproducing population of any diploidorganism, in which the relative frequency of an autosomal gene A is x.
The effective size (Ne) of the population may be defined by the relation:
N e=x(1-x)/(2VB',,) ,where VB'" is the variance of the deviation (a'x) of the gene frequency
due to random sampling of the gametes in one generation, (assuming thatx is neither zero nor unity).
If, in each generation, the population is produced by the union of Na
male and N" female gametes taken, as random samples, from all thegametes produced equally by N", members of the previous generation, sothat the generations n~ver o7erlap and the population retains its npmber
N. for many generations, then the effective size is equal to its apparent
or total number (N,..) :Ne=N" .
But, there may be cases, in which the population in every generation
emerges from any random portion of the previous generation, with theresult that the number (Nb ) of the effectively breeding individuals will become smaller than that (N",) of the total population in any stage of the life
cycle. In such case the effective size is equal to N b and smaller than N a :Ne=Nb<Na .
If there are changes in the number of the effectively breeding individuals,
as well as in apparent size, the mean effective size over ~ generations
approximates towhich is reduced toN.=~ j±(ljNb(t») ,t-l

if the change is cyclic such that N,,(T+l) = N a (I). Here it must be as;;umedthat ~ is not too large. Therefore, when there are fluctuations withina very wide range, the effective size is controlled much more by thesmaller phase than by the larger.
If there is a great difference between the number of males (N.,,) andthe number of females (NJ ), N e is much smaller than the total number,as will be shown below: Let M and W be the mean and the variancein the number (J) of female;; which mate with ,one male respectively, soNmthat M=N,/N", and W=2:,(Jt-M)2jN.", then
t=1

58

•

assuming that the number of the females is larger than that of the males(NJ>Nm ) and that a female never mates with more than one male, as
may be the case in the harems of seals. Thus if NJ is very large,
while N m is much smaller, the effective size becomes approximately
4Nm.

So far we have assumed that the frequency distribution in the numberof surviving offspring produced by one parent corresponds approximOately
to the POISSON series.
In organisms which reproduce by apomixis or close inbreeding, theeffective size is largely controlled by the variance (V) in the numbers of
the surviving offspring per individual. For example, in the populationsof self-fertilizing plants
N.=NaN b/2{(V/X-l)Nb+Na} ,where X and V are respectively the mean and the variance of the numberof surviving seeds of any individual which belongs to any effective portionof the population from which the next generation starts. The formula
reduces to N.=N/(2V), if X=l and therefore Na=Nb=N. In thefollowing, the symbol N is used for designating the effective size whenN b coincides with N a • In partially self-fertilizing plants, if ,l is' theprobability that any ovule would be fertilized by a pollen randomly. extracted from the whole population,2(1+,l)N.- ,l(4-,l)+(2-,l)2V '

N, -

I

assuming that the population retains its size N for many generations.
For a large population ,l may safely be taken as the relative frequencyof cross-fertilization.
In many higher animals and in perennial plants, generations overlap
and situations may be more complicated, so that some extention of the~bove ~ntioned definition will become necessary.
If (Jx -is the rate of change in gene frequency due to mutation andselection per one breeding season, the extended definition is:
N.=x(1-x)/{2(1-p.,a)V6'x} ,whereV6 ,x is the sampling variance of gene frequency which will be
expected in periods during which a newly-born individual ends its life andis replaced by its offspring, while (l+a)(Jx is the rate of change in -genefrequency due to mutation and selection in the corresponding periods'.
For exaIQ.ple, if every newly-born individual keeps its original fecundity
throughn "breeding seasons, and then is replaced by its offspring,59

V6/z=~~;:)[(1+~yn

-1J

and

]
a=-;;1[(1+-;;1)"-i -1,

where Nn is the total number of breeding individuals in the population.
So when n is large
N,e- (

Nn

1+ e~1 )(e2 -1) ,Le., the effective size would be about 1/(e2 -1) or 1/6.4 of the total of
breeding individuals in the population. On the other hand, the propertiesof large, uniformly distributed populations have been discussed in detailby WRIGHT (1946-1951). No doubt, "effective size" is a very importantconcept, but for the genes which influence-or have some relation to--the breeding behavior, routine extrapolation must be avoided, and newcomputations, fitted to each case, become necessary.

7. On the Process of Decay of Variability due to Random
Extinction of Alleles(Report by Mota KIMURA)

In a population of restricted size, the relative frequencies of genes
undergo random changes from generation to generation owing to therandom sampling of gametes in reproduction, so that a gradual decreasein genetic variability of the population is to be expected, unless variants
are constantly supplied by mutation or migration. The process of suchchanges was studied by FISHER (1930) by means of a partial differential
equation and also by functional equations. WRIGHT independently investigated this problem, first (1931) by the method of an integral equationin conjunction with his path coefficient technique, and later (1945) by apartial differential equation of a somewhat different kind. The attentionof these authors, however, was restricted to the state of change, after thelapse of a sufficient number of generations, when the distribution. curve
would have reached a constancy of form and the frequencies of all heterallelic classes were decreasing approximately at the rate of 1/2N. The
present writer has attempted a more extensive analysis of the problem which
includes the process before such a state is reached, and he has obtainedsome new results by calculating the moments of distribution.
Consider a population of effective size N, in which the initial frequenciesof gene A and its allele A' are p and q(=1-P) respectively. If ft(X) isthe probability that the frequency of A will change to x after t genera.
,tions, x may take anyone of a series of values:
12
10, 2N' 2ii'
1- 2N , 1,60"

and the n·th moment of the distribution about zero as origin:
1

IJ.n'(I)= 2:. x nf t(x) ,"'-0is, for a value of t which is large, and not smaller than the order of N,
IJ.n'(I)=P_3P n-I,( I...:...SP (P_ )(n-2)(n-I) 11
qn+I 1q
q (n+I)(n+2) 112-7pq(-Spq+I) (n-3)(n-2)(n-I) ,(a'-9pq(14pq2-7pq+p-q)(n+I)(n+2)(n+3)X(n-4)(n-3)(n-2)(n-I) ,( '+0(,( ')(n+l)(n+2)(n+3)(n+4) 4
5,

1
3
6
10
IS
, ,(2=1- 2N' ,(3= l-2N' ,(4=I, ,(6=I,
2N
2N
2N
etc., and the absence of ~y systematic pressure (Le. mutation, migra·
tion and selection) is assumed.
Thus the probability of fixation of the gene A in the population in thet·th generation isfi(I)= p·-3Pq,(l'-SPq(P-q),(2'-7pq( -Spq+I),(l-9pq(I4Pq2-7pq+ p-q),(/+0(.(6 t )and the probability of extinction isfi(0)=q-3pq,(l t +S pq(P-q)'(2 t -7 pq( -Spq+ I)U+9pq(I4pq2-7pq+ P-q),(4 t +0(,(5 t ) ,while the probability of coexistence of A and A' in the population; Ot=
2:. fi(x) , is0<"'<1Ot=6pq,(lt+I4pq( -Spq+I),(3 t +0(.(6 t ) .
where

,

,(1=I-

From the above relations, the following formulae will be easily obtained :(1)
Ot>Ot+1>" ·>0_=0(2)
limt..._ (Ot+1/0t)=I-I/2N
(3)
(4)
(S)

fi(x) '" 6pq(I-I/2N)tfi(l) '" P-3pq(I-I/2N)tfiCO) '" q-3Pq(I-l/2N)t(t~oo, O<x<I)(t~oo)(t-~oo)8. Process of Recombination of Chromosome Segmlmts ina Random Breeding PoPulation(Report by Moto KIMURA)•

Case of "Introgressive hybridization" (d. E. ANDERSON 1949)
In natural populations, chromosomes or gene blocks may often be
mtroduced from the populations of allied species. or subspecies through(1)

61

hybridization, though in very low frequencies. If the hybrids are moreor less fertile, the parts of the newly introduced chromosomes will spreadin the population through repeated backcrossing and crossing-over, increasing or decreasing according to the degree of fitness of the group of genesthat they contain, or to the chance survival or extinction in reproduction. The writer has investigated mathematically the behavior of suchsegments in a large and randomly breeding population and has derived
some formulae regarding the frequency distributions of such segments,
by solving integral equations of the finite difference type.
Consider a very large and randomly breeding population and let A bea type chromosome in the population while A' is an introduced chromosome which is homologous to A but differing in many alleles and having
a: genetical length of lOOxo units.
If the intial frequency (R o) of A' in the population is very low (Ro<l),the composition of the population after n generations may be expressed
approximately as:(l-Qn-Rn)AA; QnAa; RnAA' ,unless n is not very large. Here a is a chromosome produced directly
or indirectly by crossing-over between A and A'. If the composition of
the population at the start (n=O) is(l-Ro)AA; RoAA'.
the frequency of AA' in the n-th generation is
Rn=(l-xo)nRo •The frequency of Aa pairs in the same generation is
Qn={nxo+ l-(l-xo)n}R o ,of which the frequency of the chromosome pair having heterozygous
segment or segments of lOOx-lOO(x+dx) is
Qn(x)dx={n(n+ 1)(1-x)n- 1 -n(n-l)(1-x)n- 2(1-xo)}R udx,

(O<x<xo).

For deriving these formulae it is assumed that the hybrid and its
descendants have a normal fertility and only a single crossing-over isallowed to occur in the heterozygous segment. But this may not be thecase in general. More usually the fertility may be lowered by hybridization and the i~troduced chromosomes will be subjected to natural selection.
In such cases, the problem becomes very difficult to treat mathematically.
But, particularly for t~e case in which the effect of reducing fertility isgeometric; i.e., where the logarithm of fertility is proportional to thelength of heterozygous segments, the present writer has succeeded inderiving a formula by solving an integral equation. This will be discussed
in a later paper.
. For the' case in which the number of the chromosomes introduced into
62

the population is small, we must consider the chance disappearance ofsegments derived from ,them,as in the case of an individual gene. Letm be the number of AI at the start; then the chance that )J chromosomeshaving the whole or a part of segments of AI will survive to the n-th
generation may be given by

-1,[
)J.

av/pn(Z)]
az
z_ 0

,

if selection is absent. In this expression, ({In(Z) is a generating function
and satisfies the relation:({In(z)==[Fo{F 1( ••• (F n_l(Z))···)}]m ,F k(z)=exp{--(I+xk)(I-z)} and xk=xo/(I+kxo).
The probability of the complete disappearance may be given by ({In(O).
In the following table, values of ((J,,(O) are listed for several values of m
Table 5~\----1·-1~13

50.273 (0.3679)*

0.020

0.002

3

0.474 (0.6259)

0.106

0.024

7

0.613(0.7905)

0.231

0.087

15

0.708 (0.8873)

0.355

0.178

* Values in parenthli!.ses are the chance of disappearance of anindividual mutant gene, the calculation of which we owe to R.A.
FISHER (1930).

and n when xo=0.3. For instance, if a foreign chromosome is introduced
into the population through an outcrossing with an allied species and if
the cross-over value is 30%, the chance that all chromosome segments
derived from it will have disappeared after 15 generations is about 71%.
If, on the other hand, there is no crossing. over, the chance is about 89%.
(2) Change in high freEtuencies
If the initial compositIon of the population is
1_AA . 1 AAI. 1 AIAI

4

'2

'4

'

the frequency of chromosome a at the n-th generation (n>1) may be
1-'-(1- xO/2)"-1[(2 -zo)/2]

while the frequency of A orAl chromosome may be equal to(1-xo/2)"-1[(2,.-xo)/4]. .

.63

Thus the frequency of heterozygous pairs may be:170)2("-1)(2:170)2
H .. =1-2( 1---2
4'
and the mean length of their heterozygous segments may be}:170// { 2- (:17
1-"20)2("-1)(2-:170)2.

9. Method of Mating-OPerators and its Application to the Studyof Partially Self-fertilizing PoPulations(Report by Mota KIMURA)(1) Mating-operators
For a partially self-fertilizing population, it is not easy to trace
mathematically the process of recombination of chromosome segmentsfrom generation to generation. To overcome this difficulty, the methodof mating-operators has been introduced. Let H.. be the frequency ofheterozygous chromosome pairs in a population of the n-th generation;then the random-mating-operator I.. is defined such that I..H .. represents
the frequency of the heterozygous pairs after the population undergoes
random mating of one generation, while the selfing-operator 11 is definedsuch that '1H.. represents the corresponding frequency after the population undergoes self-fertilization of one generation. Thus 'I/..H .. represents
the frequency of heterozgous pairs in the (n+2)-th generation when
random-mating in the n-th generation is followed by self-fertilization inthe (n+ l)-th generation.
In a partially self-fertilizing plant population, if tt is the proportion ofindividuals fertilized by their own pollen, while ~(= 1- tt) is the proportion in which they are fertilized by polleh randomly extracted from the
population as a whole, then the frequency of heterozygous pairs in then·th generation will be

H"=(A/,,,,+tt/I)"Ho.
In expanding the right-side of (1. 1), we must notice that while theoperators follow the distributive law;
(1. 1)(1. 2)(~/oo+tt/l)(~/oo+tt/l)=~2/oo2+~ttloo/l+tt~/tfoo+tt2/12 ,they do not statisfy the commutative law;
(1. 3)
Itfoo::f=I../l .
For the calculation, the following relation is fundamental :(1. 4)
18oo1 +B+ rHo;;;:,Nf..(fl/)HoZl8oo rHo ,I. rwhere Ilf denotes the product of s It operators and r I .. operators in an
I.r64

arbitorary order. The equaiity in the formula holds only when crossingover is absent.
(2) Application to a partially self-fertilizing population.If the initial population is exclusively composed of individuals having
AA' chromosome pair (genetical length of 100xo units), we obtain bydirect calCulation,(2.1)

flif""r Ho=2- i (1+ix o)-21- { 1-;oy(r-l)(!=./°Y(1':2:1).

After expanding the right side members of (1. 1) and applying thefundamental inequality formula (1. 4) together with (2. 1), we obtainlimH" =_~~L~(1+~-~xo)<2'«1+xo),n~~2.<+.u2'<+.uif xo is not too large.
In this limiting state, it is proved that the population contains only
aa-heterozygote and aa-homozygote. Here it is the chromosome derived
from A and A' through crossing-over. In some cultivated plants, forexample in wheat, egg plant and pea, which reproduce almost exclusively
by self-fertilization, the incidence of natural cross is very rare ('<<(1).
In such cases, from the above formulae, the amount of heterozygosis inthem may be expected to be correspondingly low.

10. Statistical Theory on the Pre- and Post-reductionof Chromosomes(Report by Moto KIMURA),

By the progress in the chiasma-type theory and through tetrad analyses
in lower organisms, it has been made· clear that each locus in. a given
chromosome has its specific frequency of equational separation at the firstdivision of meiosis. The purpose of the present investigation is to deduce
mathematically the state of chromosome reduction from the experimental
findings; i.e., (1) to obtain the frequency distribution of the length ofpre- and post-reductional segments in the chromosome tetrads, and (2) tocalculate the mean length of such segments for some genetically wellstudied chromosomes.
1) For telomitic chromosomes with a genetical length of 1001 units
and without chromatid interference, the frequency distribution curve ofthe length (E) of post-reductional segments is given by the following
formula, if multiple cross-overs are negligible in frequency:
0(E)= ql'(EH2ql(l-E)-(l-E)ql"(E)-1 ,where ql(E) is the recombination fraction between two genes which arelODE units apart. For the X-chromosome of DrosoPhila melanogaster (7065units in length), the above formula becomes(J)(E)= cos 2E+2 cos (1.4-2E)+(1.4-2E) sin 2E-1 ,if 9'(E)=(sin2x)/2 (d. LUDWING 1935).
: 2) Taking the chromosome as the abscissa and assuming that f(x) represents the Probability of the post-reduction of a point x, then the mean
length of post-reductional parts of the chromosome or chromosome segmentab is
L= ~:f(x)dx,

which equals the area bounded by the curve Y=f(x), the axis of x andthe ordinates x=a, and x=b. The proportions (in percent) of the mean
length of pre- and post-reductional segments calculated by the above
method are listed for some genetically well-studied chromosomes asfollows:
Table 6Chromosomes

length ofSource of data Relative
pre-reductional
used for thesegment
calculation(l - L) + l

Neurospora crassa, C.C. LINDEGREN 1936
sex-chromosome
Sphaerocarpus
Donnellii,squami/erachromosome
Drosophilamelanogaster,
X-chromosom'l
II-chromosome

Drosophila virilis
X-chromosome

Relative length ofpost-reductional
segtnentL+l

66.5%

33.5%

E. KNAPP 1937

52.2%

47.8%

{LUDWIG 1935
CHARLES 1938

46%
48%*

54%
52%*

LUDWIG 1935

48%

52%

1CHINO, 1941; DEMEREC

40.7%

59.3%

lFUJII 1941

40.0%*

60.0%*& LEBEDEFF 1934

* The values with the asterisks have been calculated on cytologicalmaps, while all other values have been derived from genetical maps.

66,

PAPERS AND BOOKS WRITTEN .
BY THE MEMBERS OF THE STAFF,

ENDC>, Toru. 1951. Paper chromotography. (Jap.). in "r. NISHIYAMA: Technical Methods in Cytogenetics". 5th Ed. Tokyo: 348-360.
FUJII, Taro. 1951. Morphologically different twins found among the offspringof a wheat hybrid. (Jap.). Jap. Jour. Genet. 26: 230-231.
FURUSATO, Kazuo. 1951. Studies on polyembryony in Citrus. (Jap.). Ibid.
26: 223-~24. .
GOTOH, Kanji. 1951. Regression analysis of fruit shape genes by means of F 1
hybrids in eggplants. (Jap.). Ibid. 26: 223.
ITO, Taro. 1951. On growth promotion activity of culture medium filtrate of
two mating types in Neurospora crassa. (Jap.). Ibid. 26: 228-229.
KIHARA, H., M. KIMURA and H. ONO. 1951. Studies on the right- and lefthandedness of spikelets on einkorn wheats. r. Proc. Japan Acad. 27: 678-683.
KIMURA, Mota. 1951. Statistical biology. (Jap.). in "Dictionary of Statistics."
Tokyo: 539-553.
- - - 1951. Mathematical population genetics. II. (Jap.). in "Recent Ad~
vances in Biology". Vol. 4, Tokyo: 310-347.
- - - 1951. Recombination of chromosome segments through continued selffertilization and the degree of homozygosis to be expected. (Jap.). Jap.
Jour. Genet. 26: 53-62.
- - - 1951. Statistical theory on the pre- and post-reduction of chromosomes. (Jap.). Ibid. 26: 175-184.
- - - 1951. Effect produced by the random fluctuation of selective value on
the long term distribution of gene frequencies in populations. (Jap.). Ibid.
26: 234.
- - - J.951. Theoretical basis of population genetics. (Jap.). Kagaku, Tokyo
21 : 154-161.
KOMAI, Taku. 1950. Semiallelic genes. (Jap.). OGUMA Comm. Vol. Cytol. Genet.
2: 14-18.
- - - 1951. "New systematics". (Jap.). in "Recent Advances in Biology".
Vol. 4, Tokyo: 348-367.
---1951. Geographic variation in the land-snail Bradybaena similaris.
(Jap.). Jap. Jour. Malac. 16: 87-103.
- - - 1951. Inheritance of coat color in cats, and question of tortoiseshell male.
(Jap.). Jap. Jour. Genet. 26: 248.
- - - 1951. The homology of the "notochord" found in PterobraDl,lhs andEnteropneusts. Amer. Nat. 85: 270-271.
---1951. On the mosaic inheritance in some mammals. Ibid. 85: 333-334.
---1951. Frequency of tongue rollers and pedigrees of tied tongu_esJn
Japan. Jour. Hered. 42: 293-297.
- - - 1951. Contributions to the evolutionary genetics of the lady-beetle,
Harmonia. II. Microgeographic variation. (with Y. HoslNo). Geneti~~
36: 382-390.
LILIENFELD, Flora A. 1951. H. KIHARA: Genomanalysis in Triticum andAegilops. X. Concluding review. Cytologia 16: 101-123.

67

MATSUMURA, Seiji.. 1951. "Introduction to Cytogenetks." (Jap.). pp. 172.
Sapporo.
-~- 1951. Mechanism of translocation. (Jap.). in "H. KIHARA: Cytogenetics". Vol. 1, Tokyo: 107-123.
- - - 1951. Improvement of sugar beet by means of triploidy. (Jap.).
Hokkaido Tensai Togyo Shinkokai, Ziho 3: 1-14.
- - - 1951. Studies on pentaploid wheat hybrids. (Jap.). Jap. Jour. Genet.
26: 211-218.
.
- - - 1951. Radiation genetics in wheat. 1. Chromosome aberrations ineinkorn wheat induced by irradiation. Cytologia 16: 201-211.
MIYAZAWA, Akira. 1951. On the sterility of Phaseolus multiftorus. (Jap.).
Jap. Jour. Genet. 26: 224.
OGUMA, Kan. 1950. The chromosomes of the dragon-fly Epiophlebia superstes
SELYS. (Jap.). Papers fro Coordin. Comm. Res. ,Genet. 2: 23-26.
SAKAI, Kan-ichi. 1950. Timing variation in microsporogenesis in Oryza sativa
L. (Jap.). OGUMA Comm. Vol. Cytol. Genet. 2: 78-80.
.
- - - 1951. Stpdies on individual selection and selective efficiency in plantbreeding. (Jap.). Jap. Jour. Breed. 1: 1-9.
.
~-- 1951. Contributions to the method of bulk-breeding' in rice. (withY. SHIMAZAKI). (Jap.). Ibid. 1: 81-85.
- - - 1951. Experimental studies on competitional variance in plant populations. (Jap.). Jap. Jour. Genet. 26: 227.
- - - 1951. Experimental studies on the significance of selection in plantbreeding. 1. Can the performance of rice-plants, directly seeded or transplanted, be predicted from those of individually space-planted plots? ' (Jap.).
Proc. Crop Sci. Soc. Japan 20: 153-156.
- - - 1951. Ibid. II. Studies on effect of neighboring plants on the performance of space-planted one in paddy-rice. (Jap.). Ibid. 20: 157-100.'
SUSUKI, Hideo. 1951. On the example of observation with reference to eutely.
(Jap.). Jap. Jour. Genet. 26: 229.
T.AKENAKA, YO. 1951. Irregular mitosis in somatic cells of the genus Colchicum.
(Jap.).Ibid. 26: 229.
'..
- - - 1951. Cytogenetic studies of Nicotiana. 1. (Jap.). La Kromosomo
9flO: 384-392.
TANAKA, Yoshimaro. 1950. Genic analysis of inheritance of the sensitivity toalcohol. (with K. TANAKA). (Jap.). OGUMA Comm. Vol. Cytol. Genet.
2: 172-176.
--~ 1951. "Elementary Geneticll." (Jap.). pp. 340. Tokyo.
- - - 1951. Problems of acquired characters, adaptation, and orthogenesis.
(Jap.). in "Modern Biology. IV. Evolution." Tokyo :64-171.
- - - 1951. Studies on hibernation with special reference to photoperiodicity
and breeding of Chinese tussar-silkworm. IV & V. (Jap.). Jour. Seric.
Sci. Japan 20: 1-9, 132-138.
- - - 1951. Unstable genes and polygenes. (Jap.). Jap. Jour. Genet. 26:
244-245.
- - - 1951. Genetical studies of the star markings. (Jap.). Papers fro
Coordin. Comm.Res.· Genet. 2: 225-234.

68

•

TSUJITA, Mitsuo. 1951. Development and heredity in the silkworm. (Jap.). in"The Recent Advances in Gene-Analysis of the Silkworm." Tokyo: 35-65.
- - - 1951. Tendency in the studies of the silkworm virus. (Jap.). Sci. Month.
Rep. 4: 39-50.
- - - 1951. Genetical and histo-cytological studies on the lethal yellow larva
in the silkworm. (with Y. UMEYA). (Jap.). Bull. Seric. Exp. Stat. 13: 329-345.
- - - 1951. Experiments conducted to determine the effects of DDT upon
sericulture. (Jap.). Ibid. 13: 387-421.
- - - 1951. Studies on the formation mechanism of the brown spots on thesui-face of the newly moulted silkworm larva and its inheritance. Ibid.
13: 565-583.
- - - 1951. On the linkage relation between Yellow-lethal and lemon in thesilkWOi"m. (Jap.). Jap. Jour. Genet. 26: 242.
- - - and Bungo SAKAGUCHI. 1951. Studies of EM., anew gene of the Eseries, in the silkworm. (Jap.). Ibid. 26: 242.
- - - and
1951. Trisomic silkworms produced by the treatment with
BHC powder. (Jap.). Jour. Seric. Sci. Japan 20: 286.

,

69

ADDENDUM
1. The Misima Branch of Hatano Tobacco Experiment Stationof the Japan Monopoly Corporation
As stated in the Annual Report No.1, the Institute is cooperating in fundamental researches for the improvement of tobacco plants cultivated in Japan.
A branch of the Hatano Experiment Station has been set up in the mainbuilding, and three researchers including Dr. Flora A. LILIENFELD· are working
on this project. Most of the botanical members of the Institute are participatingin the work. In 1951. the following items were chosen for the main research
topics :1. The nature of the so-called good quality in tobacco,
2. Physiology and ecology of various strains of cultivated tobacco plants,
3. Interspecific crosses,
4. Artificial induction of new mutants,
6. Virus infecting tobacco plants.

,
I

2. The Association for the Propagation of the Knowledgeof Genetics (Idengaku Hukyu-kai)This association was organized on May 23, 1947, and named the Genetics
Research Institution (Idengaku Kenkyu-syo), with its office in the Laboratory of
Animal Husbandry in Tokyo University. This is the fore-runnel' of the National
Institute of Genetics. After the establishment of the Institute, the name of
the Association was changed to the present one, and the office was moved into
the InstituteNovember 1950. At that time, the primary object of the
Association was redefined as the popularization of genetics. Its activity in 1951
consisted in:1. Manufacture and distribution of microscopical slides for cytologicaldemonstration,
2. Distribution of seeds of hybrid plants,
3. Distribution of some mutant strains of Dro8ophila,
4. Editorial business of the popular journal "Iden".

in3. The Whole-Japan Association of Poultry Genetics
This association was organized by poultry breeders of all districts of Japan
with the object of producing breeds of high egg production. It has 271 regularmembers, 30 associate members and 50 special members. Since this object canhardly be realized without being guided by sound genetic principle, and without
sufficient knowledge of the genes governing egg production, the whole work has
been entrusted to the Institute. TANAKA has taken the responsibility of thewhole project. He laid out the program, and has been looking after the workin operation. By the fall of 1951, all the equipment including a hatchery, atesting barn, 6 colony barns and a residence, had been completed, and the work
was started, using 7 strains of single-comb White Leghorn and 3 strains of
Plymouth Rock. Crosses were systematically made among these, and theprogeny is being raised.

70

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