bluuebunny/crossref_metadata_2025 huggingface dataset:
Periodic reversal of heart action in the silkworm moth and pupa
Authors: Gerould John H.
Published: February 2005

Direction of peristalsis of the dorsal vessel in prepupa, chrysalis, and adult of Lepidoptera is not constantly forward; phases of forward peristalsis alternate with phases either of backward peristalsis throughout the whole dorsal vessel or of diverging waves originating in the third to fourth abdominal segments, proceeding backward and forward. Periodic reversal in the silkworm begins twenty‐four hours after spinning, forty‐eight before pupation. Pupation occurs during a vigorous backward phase. Soon after pupation, and sometimes during pupation, backward phases consist of diverging waves. Later, and in the adult, complete reversal intermittently occurs. Backward phases in the pupa are long (e.g., fifteen minutes), the average rate slow and variable, quickening at eight to ten days to that of the adult. Any long backward phase shows a gradual slowing down, except approaching pupation when the pulse quickens to equal that of forward beating. Average rate of forward beating is constant at constant temperature, but absolute rate in a long phase gradually slackens. Pauses (sometimes one and one‐half hours long in older pupae) often follow forward phases. Alternating phases in the adult, compared with the pupa, are short, about one minute and usually less than one hundred beats. In old moths the phases become still shorter, often being reduced to single beats. Opposing waves occasionally conflict. Periodic reversal occurs for hours after excision of the dorsal wall with the pericardium and heart. As in ascidians, back pressure cannot explain reversal.
Some phases in the embryonic development of Diacrisia virginica fabr. (Lepidoptera)
Authors: Johannsen O. A.
Published: February 2005

The cells of the blastoderm which are to form the serosa are two‐ to four‐nucleate; the smaller cells of the embryonic rudiment, uninucleate. The band‐like embryonic rudiment encircles the yolk at the equator of the egg. The amnion does not begin to form until after the serosa completely covers embryo and yolk. The epithelium of the midgut arises from cells situated at the tips of stomodaeum and proctodaeum. These cells, though not differentiated from adjacent ectoderm at the time of the invagination, are nevertheless interpreted as part of the preprimordium of the endoderm. In the eighty‐four‐hour stage a fold of amnion grows over the dorsal side of the embryo, entirely covering it in the course of the next few hours. A portion of the amnion thus forms the dorsal wall of the embryo. At the completion of the amnion the embryo rotates so that its ventral side is directed toward the egg center. The amnion raptures just before the larva begins to feed on the yolk which still remains around it. The serosa is consumed before hatching, which takes place about five and one‐half days after deposition.
The formation of the sex glands and germ cells of mammals. III. The history of the female germ cells in the albino rat to the time of sexual maturity
Authors: Hargitt Geo. T.
Published: February 2005

The entire ovary, including its germ cells, is produced by a local proliferation of peritoneal cells. The germ cells of the embryonic ovary grow, divide, become grouped into nests, pass through synaptic changes, and become primary follicles by three days after birth. At that time, growth of all the ova and follicles begins, and this results in a normal maturation, then a degeneration of all the ova by about thirty‐two days after birth; few, if any, of the original germ cells remain after this degeneration. About twenty‐three days after birth, there begins a great activity of the germinal epithelium in forming new ova, reaching its maximum between thirty‐six and thirty‐nine days, but continuing into the adult animal.

The definitive ova of the adult are transformed peritoneal (germinal epithelial) cells formed anew during the late youthful and adult life. This occurs chiefly by a local enlargement of single germinal epithelial cells which become surounded by follicle cells and push into the ovary; there is also the production of ova from ingrowing cords of the surface layer of the ovary. The original germ cells pass through synapsis and other meiotic changes in late embryonic and early postnatal periods, but these all degenerate; synapsis cannot be distinguished later than three days after birth. But it is possible to follow, in young and adult ovaries, the transforming germinal epithelial cells into ova which pass through normal maturation and ovulation; therefore, these must be considered as true ova, which they are in fact, even though synapsis cannot be observed in their history.
Cytological studies on the spinning glands of the larva of Galleria mellonella: Respective rôles played by the nucleus, the Golgi apparatus, and the mitochondria during secretion
Authors: Wu Chao‐Fa
Published: February 2005

Spining in Galleria begins shortly after hatching and continues throughout larval life. The gland cells secrete continuously, irrespective of the act of spinning.

The nucleus plays a direct and an importnat rôle in silk secretion by the migration of nucleoli into the cytoplasm, where they enlarge and synthesize a fatty material in the center; the fatty material is transformed into a non‐soluble basophllic substance, which then changes into the secretory product in its final form. The processes of converting the fat into non‐soluble substance and of converting the latter into the secretory product progress inwardly from the periphery of each secretory body. The secretory bodies or masses of secretory material break up into smaller and smaller masses and eventually into a fine dispersed state before their entrance into the lumen of the gland.

The mitochondria are granular in the cells of the conductive portion and filamentous in those of the reservoir and secretory portions of the gland. In the secretory portion they are orientated with the long axis toward the gland lumen. Their rǒle in silk secretion is negligible or at most a minor one.

The Golgi apparatus is in the form of discrete ring‐ and half‐ring‐shaped bodies and remains so during all stages of secretion. If it plays any rǒle in silk secretion, the fact has not been detected by the author.
Studies on the lymph system of digenetic trematodes
Authors: Willey Charles H.
Published: February 2005

A survey is made of the literature pertaining to lymph systems of the various groups of trematodes in which they occur, together with descriptions of the lymph systems in several forms not previously studied. The author reports the presence of a lymph system in two families, Cyclocoelidae and Heronimidae, which heretofore were considered to be without such organs, and the significance of this characteristic feature of certain trematodes is discussed as bearing on the problem of the evolution of monostomes, amphistomes, and other distomes. The gross morphology and the histology of the structural units of the system are described for Paramphistomum stunkardi, an amphistome from a fish, and for Diplodiscus temporatus, an amphistome from an amphibian, together with observations on the ramifications and structural components of the system in Cotylophoron cotylophorum. Various theoretical considerations concerning the development, function, and taxonomic and phylogenetic significance are treated on the basis of the morphology of the system and its resemblance to certain components of the vascular system of higher forms. The lymph system in trematodes is the natural starting‐point in any study of the phylogenetic development of vascular systems.
Metamorphosis in the honeybee
Authors: Oertel E.
Published: February 2005

Histological changes which occur in the digestive system and its appendages and in the muscular system of the honeybee during metamorphosis are described. Some attention is given to changes which take place in the fat‐body, the silk‐glands, and the reproductive system. Material of known ages was used. Observations began with the sealing of the larva in its cell and were concluded with the young bee ready to emerge from its cell. Soon after the larva is sealed in its cell, the body tissues begin to undergo a change. Larval epithelial cells lining the midgut are cast into the lumen and they are replaced by cells which proliferate from the imaginal or ‘replacement’ cells. In the fore‐ and hindgut the lining of the larval cells is replaced by imaginal cells whose points of origin are probably at the anterior and posterior ends, respectively, of the midgut. While the imaginal lining is being formed, the opening from the midgut into the hindgut is closed by a small portion of tissue. A part of the larval muscles are histolyzed and then re‐formed from imaginal myoblasts, other larval muscles disappear entirely. The strictly imaginal muscles (e.g., leg muscles) are formed by myoblasts which congregate at the point of muscle formation. There is no evidence of phagocytosis in the honeybee during metamorphosis.
The effects of breed on the growth of the chick embryo
Authors: Byerly Theodore C.
Published: February 2005

The growth of chick embryos of heavy and light breeds and the reciprocal crosses between them is described. The embryos of the heavier breed and the hybrids were found to be somewhat heavier than the embryos of the lighter breed from the tenth day of incubation to hatching time. In eggs of the same weight from the two breeds the size difference tends to disappear toward hatching time, probably due to the equivalence of the strictly limited food supply. It is pointed out that the size difference is more probably due to difference in the proportion of cells dividing at a given time than to a difference in duration of mitoses.

The mortality of the hybrid embryos was intermediate between that characteristic of the parent breeds, while the percentage of monsters in the hybrids was less than that for either parent breed. There is thus some indication of heterosis.
A study of chromatin diminution in Ascaris and Ephestia
Authors: Fogg Lloyd C.
Published: February 2005

The process of ‘chromatin diminution’ may be said to be a casting off of chromatic material from the chromosomes earlier or later in the course of mitosis. A study of the phenomenon as it occurs in Ephestia and Ascaris shows it to be comparable in only the broadest and most general sense.

In Ephestia the diminution substance is not formed in the nucleus, but is due to a later differentiation of the chromosomes long after their discharge from the nucleus. This can be made apparent by the use of differential stains and by other methods.

In Ascaris diminution is found not to occur until the third cleavage, and then in all three cells that are destined to be somatic. The diminution process in this instance is apparently comparable to the casting out of residual substance which occurs when the nuclear vesicle breaks down in other cells.
The formation of the sex glands and germ cells of mammals. V. Germ cells in the ovaries of adult, pregnant, and senile albino rats
Authors: Hargitt Geo. T.
Published: February 2005

Ovaries of adult albino rats were studied, the following phases being considered: Eleven to twenty and one‐half days pregnant, shortly after fertilization, oestrus, not pregnant, young sterile, old, and senile. Some new ova are produced from the germinal epithelium during pregnancy and oestrus, but it is in the ovaries of non‐pregnant animals between oestrous periods that the germinal epithelium is most active. There can be no question of the formation of new ova during adult life, for there is a correlation between the activity of the germinal epithelium and the number of oocytes and young follicles present in ovaries. Also one can trace the origin of ova in the surface and follow their transformation and movement into the ovary proper. In some sterile young animals little new formation took place, in others a good deal. In old and senile animals the germinal epithelium continued to be active, especially in producing ingrowing cords of cells, but frequently these were anovular. The germinal epithelium may form different types of cells by ingrowth: ova, follicle cells, and interstitial cells, but the formation of anovular follicles at one period does not prevent a later production of normal ova and follicles.

Some new ova are produced from the germinal epithelium of ovaries during pregnancy and oestrus, but it is in the ovaries of non‐pregnant animals between oestrous periods that the germinal epithelium is most active. There can be no question of the formation of new ova during adult life, for there is a correlation between the activity of the germinal epithelium and the number of oocytes and young follicles present in ovaries. In some sterile young animals little new formation took place; in others, a good deal. In old and senile animals the germinal epithelium continued to be active, especially in producing ingrowing cords of cells, but frequently these were anovular. The germinal epithelium may produce different types of cells by ingrowths—ova, follicle cells, and interstitial cells—but the formation of anovular follicles at one period does not prevent a later production of normal ova.
Effect of composition of air on the growth and mortality of the chick embryo
Authors: Romanoff Alexis L.
Published: February 2005

The fertilized hen's eggs of known origin were incubated under predetermined, standardized, and uniform conditions of all physical factors except air, the composition of which in respect to the carbon dioxide and oxygen varied in each experiment. The growth and mortality of the embryo were studied daily, with, on an average, four observations.

The experimental data show that the continuous exposure to about 0.4 per cent of carbon dioxide in the air of the incubator stimulated growth during the first part of embryonic life. A high content of carbon dioxide and at the same time a slightly reduced content of oxygen resulted in diminishing of the size and increasing of mortality of the embryo. The maximum combined proportions of these gases possible for growth of the embryo were about 22.0 and 16.3 per cent, respectively. A temporary exposure (twenty‐four and forty‐eight hours) to a large amount of carbon dioxide resulted in diminishing the size of the embryo without apparent deformities or increase of mortality.
The embryogeny of the Polyctenid, Hesperoctenes fumarius Westwood, with reference to viviparity in insects
Authors: Hagan Harold R.
Published: February 2005

Four functional types of viviparity are recognized, and the last, pseudoplacento viviparity, is illustrated by a review of the embryogeny of a species of Polyctenidae. This insect normally has ten embryos in the reproductive tract in successive stages of development. The problem of fertilization is discussed, for there seems to be no spermatheca and spermatic clumps are present in the haemocoel. No organ of Berlese can be found. One, apparently a nymph, when sectioned revealed spermatozoa in even greater abundance than the mature females. Four to six of her offspring would seem to be paedogenetic.

Females liberate ova that are yolk‐free, and no chorion is secreted about them. Blastomeres are distinct, the embryonic envelopes are formed as usual, and hemipteran embryology occurs. The trophserosa functions until blastokinesis takes place, when the pleuropodial extensions evaginate and encompass the embryo which now lies in a pleuropodial cavity. The pleuropodia function as Lutrient organs, or psedoplacenta, until shortly before birth. At birth the embryo is a little more than one‐third the adult body length and bears strongly developed setae.
Life cycle, sex differentiation, and testis development in Melanoplus differentialis (Acrididae, Orthoptera)
Authors: Nelsen Olin E.
Published: February 2005

The general morphological and histological evidence accumulated by this study suggests the following facts:

Under out‐of‐door conditions, in the vicinity of Philadelphia, Pennsylvania, embryonic development begins at deposition and continues to the middle or late spring, when hatching occurs. The postembryonic development is completed during the summer. Copulation and oviposition occur in the late summer and early fall.

The embryonic development may be divided as follows:

The prerevolution period, in which the rudiments of organs and systems are formed.

The early‐revolution period, during which the direction of the embryo in the egg is reversed.

The late‐revolation period, or time of yolk circumcrescence and completion of the dorsal wall of the embryo.

The postrevolution period. comprising development from yolk engulfment to hatching.

The sexes are differentiated during the early‐ and late‐revolution periods.

In the differentiation of the genital rudiments, a) the germ cells are segregated into groups; b) and indifferent mesodermal element grows in among the germ cells of such a group; c) the processes of this cell (the apical cell) form intimate connections with the processes of connective‐tissue elements surrounding the germ‐cell group; and, d) the covering membrane of the genital rudiment grows in between the various germ‐connective‐tissue cell groups, completing the rudiment of the follicle.

When the adult condition is reached the testis is functionally differentiated.
The development of the carp, cyprinus carpio. I. The larval life of the carp, with special reference to the development of the intestinal canal
Authors: Smallwood W. M. , Smallwood Mary Lovett
Published: February 2005

The detailed spawning habits and hatching period are described. The larval period is divided into the inactive, when the yolk is the source of food, and the active period, when food is captured. The rate of growth and transformation of the larvae into fry is described.

The cell formation passes into a syncytial period, when there are produced many nuclei without cytoplasm.c division. Around these nuclei, the cytoplasm collects to give rise to more cells. The method by which mucous cells are produced is described and also the presence of secretion masses in both the mucous cells and the syncytium of the mucosa.
The development and the regeneration of the color pattern in brachydanio rerio
Authors: Goodrich H. B. , Nichols Rowena
Published: February 2005

The teleost fish Brachydanio rerio is strikingly marked with longitudinal black stripes, which extend into the caudal fin and across the anal fin. Removal of the anal fin is followed by complete regeneration of the fin and of its normal color pattern. Microphotographic studies show that melanophores are at first uniformly distributed in the regenerating tissue and that later the melanophores disintegrate in the zone of the future light stripe and increase in the region of the future dark stripe. Observations on the normal development of the fin where the history of the individual melanophores has been followed show the same mode of formation of the stripes.
Modified mitosis in the chick embryo
Authors: Stough Howard Brown
Published: February 2005

A study of cell division in the chick embryo has revealed in striated muscle and in the early stages of all the principal tissues and organs a process, followed by the greater percentage of the dividing nuclei, which resembles amitosis, but is undoubtedly a highly modified form of mitosis. This process is designated ‘modified mitosis’. The belief that this is essentially mitotic rests upon the fact that a number of discrete bodies may be distinguished in the one or two chromatin masses of each nucleus. These masses, or ‘mulberries’, might easily be mistaken for nucleoli or karyosomes were it not that they exhibit division by elongation and constriction. These structures probably represent masses of minute and closely clumped chromosomes in somatic number dividing in a qualitative and a quantitative fashion. As additional evidence there are present between the dividing mulberries exceedingly fine fibers which possibly represent an attempt at spindle fibers. Neither centrosomes nor asters are present, but since, if present, they would have to be of the intranuclear variety (the nuclear membrane never disintegrating) their absence is immaterial. The nucleus divides not by constriction, but by the formation of a nuclear plate. This process of modified mitosis is probably a device which favors the speed of nuclear proliferation necessary to such rapidly growing tissues.
Insect development. IV. External morphology of grasshopper embryos of known age and with a known temperature history
Authors: Slifer Eleanor H.
Published: February 2005

Eggs of Melanoplus differentialis, a grasshopper, secured immediately after they had been laid, were placed in a water bath kept at 25°C, and allowed to develop for definite periods. After fixation, the embryos were dissected out of the eggs and drawn. Large numbers of eggs were examined in order to determine the degree of variation under specific conditions. For the stages following revolution, eggs were used in which ‘hibernation’ had been prevented by exposure to low temperatures.
The spermatogenesis of the mouse (mus musculus, var. albula)
Authors: Cutright Paul R.
Published: February 2005

The previously reported diploid number of forty chromosomes has been verified; the sex chromosomes have been shown to exist early in the growth period and to be of the X‐Y type; and a chromosome‐nucleolus has been described in the resting stage of the primary spermatocytes which persists throughout synapsis and divides at the time of diakinesis into two parts that are equal in size and are thought to be the largest pair of autosomes. The diakinetic bivalents have been described rather fully. These are short and heavy and assume a great variety of shapes, the most characteristic of which are ring, V, Y, cross, and hexagonal. The union of bivalents during diakinesis has been shown to be an intimate one; in every instance first chromomere unites with first chromomere or third chromomere with third chromomere. This is considered to be significant evidence of the allelomorphism of chromomeres in mammals.
A study of the Golgi elements
Authors: Nahm Laura J.
Published: February 2005

This investigation was undertaken to determine some of the variables involved in the demonstration of the Golgi elements. Gland cells of vertebrates were studied vitally, after impregnation by osmic acid methods, and after autolysis.

The duration of the staining period and the concentration of the stain condition the results obtained by vital staining with neutral red. The success of impregnation of Golgi elements with osmic acid varies with,(1) the type of tissue, (2) the time of initial fixation in relation to the time of the death of the animal, (3) the position of the cell in the piece of tissue, and, (4) the temperature of incubation with osmic acid. Stages in the impregnation of Golgi elements can be followed by examining preparations of the same tissue at frequent intervals during the incubation period. An increase in the amount of material which reduces osmic acid and which may form Golgi elements occurs in the cells during autolysis.

The results are interpreted as indicating that Golgi elements are visible products of chemical reactions that occur in cells. They represent localized regions containing particular classes of chemical compounds which may be present, as such, in living cells or result from transformations in the cells during incubation. It is suggested that for the cells under consideration these substances may be unsaturated fatty acids.
The inheritance of cataract in man, pedigree and interpretation
Authors: Hornback Edward T. , Garis Charles F.
Published: February 2005

From a mating of first‐cousins, of whom the female had cataract, there issued in four generations a progeny of 138 individuals, 33 of whom had cataract (23.8 per cent). Discounting the last generation, about which little is known, also discounting other unknown members, there were 29 known unaffected, 30 known affected, i.e., 50.8 per cent had cataract. The pedigree by generations shows that cataract is inherited as an autosomal (Mendelian) dominant. However, the mode of inheritance is atypical in that the defective gene for cataract may be borne, and is so borne because transmitted, without producing in the bearer its characteristic defect. In the second generation there were four of a family of nine with cataract; of the five without cataract two produced cataractous offspring and three did not marry. The literature is replete with pedigrees in which cataract is inherited as a typical autosomal dominant; there are a few pedigrees (four are reproduced) in which the mode of inheritance, while distinctly that of an autosomal dominant, resembles the present pedigree in being atypical. It is concluded that cataract is inherited as an autosomal dominant, but that in some cases it is produced only under certain conditions. These conditions are as yet not definitely known. Clinical writers seem to favor the view that nutritional and endocrine disturbances predispose to the realization of the defect.
The rudimentary copulatory organ of the domestic fowl
Authors: MacDonald Elizabeth , Taylor Lewis W.
Published: February 2005

The rudimentary copulatory organ of chickens was first observed as a phallic knob in 6‐day embryos. This phallic knob enlarged similarly in both male and female embryos up to the twelfth day: from the twelfth to the seventeenth day it was distinguished by a large process in the males and a diminishing process in the females. Further differentiation took place from the eighteenth to the twenty‐first days: some females lacked the porcess, others retained a smaller process than that of the male. As growth advance, fewer females retained the process until at 12 weeks of age it had entirely disappeared. The process was found in all males and showed no retrogression, whereas the few capons examined lacked it. A ridge‐shaped ‘pseudo’ process developed at about 1 week in some females and was present up to 3 weeks of age. Histologically and embryologically, the process was seen to possess some characteristics of a penis. The cloacal method of sex determination might be used with an average maximum accuracy of about 90 per cent in living day‐old chicks.
The anatomy and blood supply of the urogenital system of lepidosteus platystomus rafinesque
Authors: Pfeiffer Carroll Athey
Published: February 2005

A description of the urogenital system in both sexes of Lepidosteus platystomus Rafinesque, and new observations on the blood supply to this system as well as to the rest of the viscera is given.

The testes resemble the true piscine type. The sperm are carried by numerous vasa efferentia to the kidney tubules, through the mesonephros to the wolffian duct, and to the exterior as in the elasmobranchs and amphibians. The most anterior of the vasa efferentia are non‐functional. The ovaries are simple sac‐like structures continuous with their ducts. The oviducts transverse the ventro‐lateral surface of the mesonephros, and enter into the dilated portions of the wolffian ducts, where they join, directly anterior to the urogenital aperture. There are no ducts in the male homologous with the oviducts of the female. The kidneys fused posteriorly, appear to extend the entire length of the body cavity, but the anterior third is non‐urinary.

By injection methods, the celiaco‐mesenteric artery is shown to be crowded to the posterior end of the body cavity by the complicated swim‐bladder, and runs anteriorly to supply the entire viscera. Its anterior portion is incorporated in the liver.
Spermatogenesis in gecko japonicus (dumeril and bibron)
Authors: Wu Su‐Hsuen
Published: February 2005

The nuclear changes involved in the two maturation divisions of G. japonicus have been studied in considerable detail. All observations compel a telosynaptic interpretation. The duality, an apparent parasynapsis, as seen beginning from synizesis up to diplotene is a result of a longitudinal splitting of the chromosomes joined end to end. Strepsinema is brought about by breaking up of the diplotene thread into segments, which really are pairs of synaptic mates in end‐to‐end union; each segment then bends at its middle to form V‐ or ring‐tetrads. There are altogether twenty tetrads. All chromosomes assume a rod shape when in the metaphase plate. A pair of heterochromosomes was observed to be slower than the rest in assuming the rod shape and in getting into the plate. The marching of the synaptic mates toward their respective poles is asynchronous. Second division begins right after the chromosomes have reached the poles. Zwischenkörper observed at the end of the second division are regarded as formed by the granules seen in the polar regions during the first division.
Studies of the epithelium lining the caeca and mid‐gut in the grasshopper
Authors: Woodruff B. H.
Published: February 2005

The alignment and condition of mitochondria in the epithelial cells indicate that secretion is apparently the chief function of the midgut and the attached caeca. In view of the response of these cells to vital dyes, and to various fixatives, other cell structures–particularly vacuoles–are uncertain evidence of cell activities. Many structures visible by means of vital dyes indicate changes in the permeability of the cell membrane, and subsequently in the cytoplasm. Hence, they are artifacts, just as truly as those found in fixed tissue.
The relationships of the medullae and cuticular scales of the hair shafts of the soricidae
Authors: Smith Helen Hoffman
Published: February 2005

Mid‐dorsal protective hair‐shafts from forty‐five species of Soricidae were studied with the object of investigating the relation between the differences in certain microscopic structural elements and the diameters of the shafts in which they were developed, and the possible occurrence of specific characters in these elements. In comparing like portions of like hair‐shafts, it was found that scale‐ and medulla‐forms were related (with slight variations within their form‐groups) to the diameters of the hair‐shafts in which they were developed. It is possible that further study of these slight variations may show them to be associated with the species bearing the hair.
The development of the ovary in the grasshopper, Melanoplus differentialis (acrididae; orthoptera)
Authors: Nelsen Olin E.
Published: February 2005

Each indifferent genital rudiment in the grasshopper embryo is composed of the following: (1) a terminal filament membrane; (2) an epithelial plate of indifferent cells, the dorsal cell mass; (3) the central cell mass containing germ and indifferent cells; (4) the ventral cell strand, and, (5) a delicate, investing membrane, the outer limiting membrane. It is roughly spindle‐shaped in transverse section and extends from the first to the eighth abdominal segments.

In the sexual differentiation of the genital rudiment the dorsal cell mass is retained as a definite embryonic rudiment in the female, but becomes an indistinguishable part of the central cell mass in the male.

Ovarian development is initiated in the dorsal cell mass area, where cell aggregations are formed. Each aggregation is ultimately surrounded by the ingrowing outer limiting membrane to form distinct cellular columns. A latero‐ventrad extension of this ingrowing process into the central cell mass continues the column formation process into the latter and results in the formation of a distally tapering structure composed of indifferent cells distad and germ cells and indifferent cells proximad. This structure constitutes the rudimentary ovariole which finally differentiates to form the terminal filament, germarium, and vitellarium.

The ovarian portion of the oviduct and the tubular connection between the ovariole and oviduct are differentiated from the ventral cell strand.
The developmental anatomy of male genitalia in Melanoplus differentialis (acrididae) orthoptera)
Authors: Else Frank L.
Published: February 2005

An investigation has been conducted to ascertain the relationship of certain structures in the embryo of the grasshopper known as Melanoplus differentialis with reproductive organs in the adult male.

The order of development of these structures was traced through the entire life history.

It was determined that they are the rudiments of certain reproductive organs and that the knowledge obtained serves as an aid in more accurately classifying insects.
The mesodermal relations of the pars buccalis of the hypophysis in the duck
Authors: Friedman Bernard
Published: February 2005

This paper describes the cellular relations between the prechordal mesoderm and the hypophyseal analage in duck embryos from the first to the eighth day of incubation.

At nineteen somites the ectoderm destined to form hypophysis is seen as a plate of cells lying under the mesodermal mass anterior to the notochord. It extends anteriorly in intimate contact with the base of the forebrain, and posteriorly for about the same distance to the oral membrane. Following the lateral growth of the prechordal mesoderm and the rapid overgrowth of the forebrain, Rathke's pouch is definitely outlined. The upward expansion of the pouch, concomitant with the lagging of some of the prechordal mesoderm in the midline, effects a very close relation between these cells and those at the tip of the pouch. With the lateral expansion of the premandibular head cavities, some of the mesoderm adheres to walls of Rathke's pouch in the form of rods or knobs. As development proceeds the inherent growth tendencies of ectoderm and mesoderm express themselves differently and the rods or knobs become constricted off from the pouch, forming in its vicinity vesicles which exhibit a definite lumen.

The question of an entodermal contribution to the hypophysis in this form is briefly considered.
Cytological studies of the epidermis of Rana pipiens and Rana clamitans tadpoles, with special reference to the figures of Eberth
Authors: Weed Isabelle Gifford
Published: February 2005

The conspicuous intracellular fibers (figures of Eberth) which are present in the basal epidermal cells of Rana pipiens and Rana clamitans tadpoles are thought to be connective tissue branches from the corium. They are not believed to represent fused mitochondria as concluded by Saguchi ('13). Their probable function is to furnish support to the basal epidermal cells and to strengthen the connection of the epithelial layer to the corium.

It is believed that fully developed tadpole skin, before the period of metamorphosis has begun, consists of only two layers of cells, although there may appear to be more. Each of these layers is believed to be self‐maintaining by mitotic division within the individual layer. The basal layer apparently does not furnish cells to the outer layer, nor was any evidence found that the outer layer is sloughed during the larval period.
The osteology of the haplimous fish Novumbra hubbsi schultz with comparative notes on related species
Authors: Chapman Wilbert M.
Published: February 2005

This paper is an attempt to clear up the confusion concerning the osteological relationships among the Haplomous fishes.

The osteology of Novumbra hubbsi was worked out by the dissection of numerous specimens. The various skeletal features found were compared with the osteology of Umbra limi, U. pygmaea, U. crameri, and Dallia pectoralis.

A description of each skeletal element of Novumbra was made, followed by a description of the chief differences between it and the same structures in Umbra and in Dallia. No constant osteological differences were found between Umbra limi and U. pygmaea, and very few between these two species and Umbra crameri. Novumbra and Umbra have more in common with each other than either does with Dallia or Esox. The presence of postorbitals, postcranials, and the shape of the secondary shoulder girdle in Novumbra show it to be also closely related to Dallia and Esox.

The relationships of the various forms are summarized in a synoptic key which lists the following groups: Order Haplomi. Superfamily I, Dallioidea; Family Dallidae; Genus and species, Dallia pectoralis. Superfamily II, Umbroidea; Family 1, Umbridae; Genus and species, Umbra limi, U. pygmaea and U. crameri; Family 2, Novumbridae; Genus and species, Novumbra hubbsi. Superfamily III, Esocoidea; Family Esocidae; Genus, Esox.
Insect development. VIII. Maturation and early development of unfertilized grasshopper eggs
Authors: King Robert L. , Slifer Eleanor H.
Published: February 2005

Maturation and early cleavage in unfertilized Melanoplus differentialis eggs have been followed with material secured immediately before as well as after oviposition, and (1) fixed at once, or (2) held in an incubator at 25°C. and, subsequently, fixed at selected intervals. Eggs ready to be laid were all found in the metaphase of the first maturation division. The second polar body is given off (at 25°C.) within 5 to 7 hours after laying. Meiosis appears to be unaffected by the absence of the sperm nucleus and proceeds at the same rate as in fertilized eggs. No morphological differences could be found between the process here and in eggs from mated females.

During early cleavage, or later, the diploid number of chromosomes may be restored in some (or perhaps all) cells of the embryo.

Development begins in the greater number of these unfertilized eggs but is successfully completed in only a very few.
A comparative study of the hyobranchial apparatus and throat musculature in the plethodontidae
Authors: Piatt Jean
Published: February 2005

The hyobranchial apparatus and throat musculature of the plethodontid salamanders are examined. The interhyoideus is thought to be the homologue of the intermandibularis posterior and the posterior part of the intermandibularis anterior. The quadrato‐pectoralis is found only in Desmognathus (Leurognathus?), and Aneides. Its presence in the former is a primitive condition; in the latter, secondary. The gularis had its phylogenetical origin as a slip from the quadrato‐pectoralis. The lingual cartilage is found only in Gyrinophilus, Pseudotriton, Eurycea, and Manculus. It is the homologue of the [sehnenplatte] of Salamandra; not the otoglossal. The presence of the suprapeduncularis and the absence of the genioglossus is not peculiar to adult free tongued genera. The anatomical evidence allies Batrachoseps with Hydromantes and Oedipus. The latter two genera are derived from ancient Plethodon stock, not from Gyrinophilus stock. Stereochilus, Typhlotriton, and Typholomolge are the degenerate descendants from ancient Gyrinophilus stock.
The excretory system of the trematode, Typhlocoelum cucumerinum, with notes on lymph‐like structures in the family Cyclocoelidae
Authors: Willey Charles H.
Published: February 2005

The exeretory system of Typhlocoelum cucumerinum consists of three pairs of longitudinal channels communicating by a single ventral vessel with the excretory vesicle. Branches subdivide extensively and anastomose forming a dense network of tubules throughout the body. The vessele possess many of the features characteristic of lymph systems as described in amphistome trematodes. They have cuticular walls, come into intimate association with the intestine and contain a granular coagulum and cellular elements suspended in the lumen. The single system of vessels appears to be functioning as a combined lymph and excretory system. Typhlocoelum americanum Manter and Williams ('28) is regarded as a synonym of Typhlocoelum cucumerinum (Rud. 1809).
The early development of the hypoglossal musculature in the chick
Authors: Hunter Russell Palmer
Published: February 2005

The hypoglossal downgrowth is initiated at about the twenty‐somite stage, as ventral extensions from the postotic (occipital) myotomes 3 and 4. At thirty somites, occipital myotomes 2, 3 and 4, and cervical 1 have developed ventral processes. These descending processes with contributions from posterior myotomes later form a common condensed area below myotomes 2 to 7, the submyotomic tract. There develops from this a cord of mesoderm, the hypoglossal cord or downgrowth.

The anterior postotic myotomes are classed as indirect (numbers 1, 2, 6 and 7) or direct (numbers 3, 4 and 5) contributors to the hypoglossal downgrowth.

Mechanical factors associated with this growth process are discussed.

The hypoglossal nerve at 75 hours has six roots, four occipital (numbers 1 to 4) and two cervical. The first two occipitai roots fail to keep pace in development and are subsequently lost. A transïtory connection of the third cervical to the hypoglossal nerve is demonstrated at the age of 5 days. At 6 days the first occipital root is reduced to scattered fibers, the remaining occipital roots, numbers 2 to 4, increase in size, cervicals 1 and 2 join the hypoglossa.

The correspondence of the myotomes providing the contributions to the hypoglossal cord and the nerves providing the major contributing roots of the hypoglossal nerve is commented on.
The postembryonic history of the somatic musculature of the dragonfly thorax
Authors: Maloeuf N. S. Royston
Published: February 2005

From the first larval instar until the time of the final transformation into the adult the thoracic muscles are numerically the same. The muscles increase in fiber number with the growth of the larvae. There are two types of larval muscles: a. functional (striated and of considerable diameter) b. non‐functional (unstriated and of narrow diameter). The non‐functional muscles are mainly the prospective wing muscles of the adult. They grow most in diameter at the time of the final transformation. The positions of attachment of both types of muscles undergo no marked replacements during transformation, although the skeletal parts to which they are attached may become greatly modified. The larva has numerically more muscles than the adult. Extensive obliteration of the trunk leg muscles and of some neck muscles takes place. The intrinsic leg muscles of both the larva and the adult are the same.

There are no anlagen of the adult muscles in the larval labium, and myoblasts probably form the adult musculature of this organ.

The wing muscles of adult Anisopterid dragonflies insert close to the articulations of the wings on apodemes arising from membranes, or on discs arising as internal invaginations of detached, lateral, tergal plates.

During the metamorphosis of its musculature, a dragonfly exhibits every essential phenomenon that a so‐called ‘holometabolic’ insect does.
Further studies in modified mitosis
Authors: Stough Howard Brown
Published: February 2005

In a paper published by the author in 1931 there was described a process of cell division called ‘modified mitosis.’ The present report adds quantitative studies of the process and a general evaluation of it and its role in the development of the embryo. Cell counts were made in various stages of chick embryos and the mitotic indices determined. In no cases can these mitotic indices account for the growth which the cell counts indicate. Periodicity in cell division in the chick cannot be established. Modified mitosis appears after careful study to be fundamentally mitotic in nature. Actual division of chromatin, nucleus, and cytoplasm occurs. Modified mitosis is not amitotic in character, but it is probable that it is what has been reported in the past as amitosis. It is very doubtful whether amitosis is found in the chick or in any of the vertebrates. Modified mitosis is part of the active phase of cell division and cannot be explained away as merely resting stages containing one or two nucleoli. It is probable that the division of chromatin nucleoli cannot be accounted for on any other basis than that of modified mitosis. In modified mitosis we undoubtedly see irreversible cell differentiation. The genetic implications of this process are not yet clear. If present interpretations of modified mitosis are in error a complete revision of our ideas of typical mitosis is in order.
The neuromotor system of oxytricha
Authors: Lund Everett E.
Published: February 2005

The neuromotor system and associated organelles of Oxytricha have been studied in living specimens viewed with dark field illumination, and in whole mounts and sections stained with Heidenhain's hematoxylin or Mallory's stain. Microdissection has also been used in some cases.

The neuromotor system has been found to consist of the adoral membranelles and coordinating fibrils, the undulating membrane and its basal fibril, two sets of cytostomal fibrils and two sets of postesophageal fibrils. The anal cirri may possibly be involved in the complex. No neuromotorium seems to be present.

Motor and feeding organelles not morphologically connected with the above system are eight frontal and five ventral cirri, and a varying number of marginal cirri. The anal cirri, if not connected with the neuromotor system, would be included here. The minute structure of each type of cirrus has been studied, and the action and probable function has been determined from studies on normal, anesthetized, and dissected individuals. A brief comparison is made between the neuromotor system and organelles of Oxytricha and those of Euplotes and Paramecium that have previously been described in the literature.
The dorsal axial musculature of certain primitive permian tetrapods
Authors: Olson Everett Claire
Published: February 2005

The development of the dorsal axial musculature is traced from Eryops, through Diadectes, to Dimetrodon. lguana, a modern form, is used for comparison. The axial muscles of a primitive form, such as Eryops, were thick, fleshy, and metameric; those of more advanced types, such as Dimetrodon, were light, highly tendinous, and largely unsegmented. Diadectes represents an intermediate stage. The changes in the muscles and related changes in the axial skeleton are closelyassociated with the development of active, terrestrial animals.
The absorptive processes in the embryos of Parabrotula dentiens, a viviparous, deep‐sea Brotulid fish
Authors: Turner C. L.
Published: February 2005

Parabrotula dentiens is a viviparous deep sea Brotulid fish. The embryos at the 6 mm. stage are held within the ovarian cavity as are the embryos of Zoarces, the Embiotocidae, the Goodeidae, the Jenynsiidae and the Anablepidae in the later stages. The embryos of Parabrotula dentiens are equipped with external processes which are attached around the anus and to the ventral wall of the embryo for a short distance in front of the anus. The processes have a spongy connective tissue stroma and are covered with a syncytial layer. It is assumed that the processes augment the body surface of the embryos and have a nutrition‐absorbing and an oxygen‐absorbing function.
The osteology and relationships of the phallostethid fishes
Authors: Bailey Ralph J.
Published: February 2005

Two genera of the Phallostethid fishes were anatomized using both the clearing and the dissection methods. While resembling Poecillids and agreeing with them in numerous anatomical features, these fish are true Acanthopterygians and apparently are correctly placed by Myers in the suborder Phallostethoidea erected for them in the order Percesoces. The two divergent types of priapia found in the group are readily derivable one from the other, corresponding bone for bone. The priapial bones can be homologized with the missing pelvic fins and girdle plus, perhaps, the post cleithrum and some of the pectoral pterygials. A comparison is made between the Phallostethid priapial skeleton and the highly modified girdle complex of the Polynemids.