bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Sterility and Prenatal Mortality in Wild Rabbits
Authors: Rogers Brambell F. W. , Mills Ivor H.
Published: April 2021

The relation of the proportion of litters showing loss to the proportion of embryos lost is discussed and is shown to vary according to the way in which the mortality is distributed. The proportion of ova lost before implantation in litters that survive varies according to the number of ova ovulated as the linear regression where x = the initial number of ova in the litter. The loss of ova before implantation in the whole sample of 12,551 ova was 1188 or 9·5%. The proportion of litters suffering loss before implantation in which some embryos survive implantation varies according to the number of ova ovulated as the linear regression where x = the initial number of ova in the litter. The number of litters suffering loss before implantation in which some embryos survive implantation in the whole sample of 2179 litters was 796 or 36·5%. Fewer litters suffered more loss than would be expected if the loss were distributed at random amongst the ova. The sample of litters showing loss is not homogenous, and the probability of loss of ova is greater in some of them than in others. In litters that suffer a loss of two or more ova there is a tendency for the loss to be concentrated in one uterus of each pair. Some or all of this tendency may be accounted for by obstruction of the uterine tract on one side. The number of animals out of a total of 2073 which had lost all the ova on one side, but not on the other, was 92, an excess of 18, or 1·8%, over the expectation on a random basis. The occurrence of loss on one side does not affect the probability of loss on the other side. Not more than 3·64% of litters are lost entirely before implantation and probably not less than 1·00%. The percentage of litters lost entirely before implantation is at a minimum in litters of an initial size of five or six, the most frequent sizes, and at a maximum for litters of the largest and smallest sizes. It is also at a minimum during the height of the breeding season, and is higher at the beginning and end. Animals above the average body weight suffer less loss of ova before implantation in litters that survive than do those below the average body weight. There is no detectable seasonal variation in the loss of ova before implantation in litters that survive. The loss of ova before implantation in litters that survive is heavier in animals with no milk in the mammary glands than in those with milk.
The Effect of Labyrinthectomy on the Co-ordination of Limb Movements in the Toad
Authors: Gray J. , Lissmann H. W.
Published: April 2021

If the limbs of an animal are to propel the body along a straight horizontal line the propulsive forces exerted by the right and left pairs of limbs must be equal and the vertical thrusts exerted by each of the four limbs must be such that their combined resultant is equal to the weight of the body and act through its centre of gravity (Gray, 1944). During the normal ambulation of a toad these conditions are not strictly fulfilled, for the body exhibits a slight but definite tendency to rotate about its principal axes (Barclay, 1946). Since all such movements are liable to induce compensatory reflexes of labyrinthine origin, it is of interest to know how far the normal level of co-ordination between the limbs is affected by labyrinthectomy. In all cases the operation has been performed from the dorsal side.
The Influence of Temperature and Humidity on Instar Length in Calandra Granaria Linn
Authors: Eastham L. E. S. , Segrove F.
Published: April 2021

In an earlier paper, Eastham & McCully (1943), the results of an investigation into the effects of temperature and humidity on the oviposition responses of Calandra granaria were published. There the effects of environment on the multiplication of cultures of Calandra were recorded in so far as that increase depended upon the rate of egg-laying, number of eggs laid and the length of ovipository life of females. An attempt is made here to extend that information, not only by showing how environment determines the total duration of a developmental period, but how it affects each separate instar of that period from the egg to the emergence of the adult from the pupa.
The Chemoreceptors of the Wireworm (Agriotes Spp.) and the Relation of Activity to Chemical Constitution
Authors: Crombie A. C. , Darrah J. H.
Published: April 2021

This paper continues the work on the responses of wireworms (Agriotes spp.) to chemical stimulation, published in a previous paper (Thorpe et al. 1947), by a further analysis of the relation of activity to chemical constitution and of food finding, and the investigation of the anatomy and physiology of the chemoreceptors. Substances present in food plants elicit two responses in wireworms, orientation and biting. There is a clear distinction between those compounds which cause only orientation and those which cause both biting and orientation. In almost every case the former have high activities (9 − 11) while the latter have activities of less than 3. All the biting compounds tested for orientation have proved active, the threshold being similar to that for biting. Substances causing orientation fall into two classes, viz. amides and urea derivatives, and dicarboxylic acids. In view of the small number of compounds tested the two classes of active substances should be treated with reserve. In the first, it seems definite that the amide group is responsible for activity. But while all the other compounds found to be active fall into the second class, i.e. are dicarboxylic acids, it is by no means true that all dicarboxylic acids are active and no rule is apparent for predicting whether a given dicarboxylic acid will be active or not. Substances causing both orientation and biting summate when either response is tested. The following pairs of substances summated when tested for the responses indicated: glucose and sucrose for orientation and biting; glucose and peptone, glucose and triolein, peptone and triolein and glucose and tannin for biting. Orientation occurs in a gradient of concentration of which the steps are formed by different substances, as well as when the steps are formed by one substance as was shown in the previous paper. Active substances are secreted in small amounts by the roots of growing potato plants. These would explain the orientation of wireworms to the roots of growing plants (e.g. wheat). It is thus likely that the root system forms an extended trap along which wireworms may be led to the grain or tuber in the centre, where a wound caused by their random biting would release active compounds in sufficient concentration for them to remain and feed. The biting of glucose is inhibited by a number of substances, viz. lead acetate, quinine, allyl-iso-thiocyanate and common salt, as well as by acid and alkaline solutions. Common salt also inhibits orientation in glucose, but not in asparagine. The chemoreceptors which appear to be involved in these responses are of two kinds : peg organs, located on the labial and maxillary palps and galeae, whose stimulation leads to both orientation and biting; and a cup-shaped sensilla on the distal segment of each antenna, whose stimulation leads to orientation only. Both asparagine and glucose stimulate both kinds of receptor.
The Functions of the Corpus Allatum in Rhodnius Prolixus (Hemiptera)
Authors: Wigglesworth V. B.
Published: April 2021

It has been shown in earlier papers (Wigglesworth, 1934, 1936, 1940) that metamorphosis in Rhodnius takes place when the corpus allatum ceases to secrete the ‘inhibitory’ or ‘juvenile hormone’. There was no evidence for the existence in this insect of a ‘metamorphosis hormone ‘which promotes the development of imaginai characters. Growth and moulting are induced at all stages of development by a ‘moulting hormone’ (what is called by Scharrer & Scharrer (1944) a ‘growth and differentiation hormone’) secreted in the dorsum of the protocerebrum. When this hormone alone is acting, the latent imaginai characters are realized and metamorphosis occurs. When the ‘juvenile hormone’ from the corpus allatum of the early nymphal stages is present in addition, it causes the preferential development of nymphal characters and thereby suppresses those of the adult.
The Physiology of Echinus Esculentus Spermatozoa
Authors: Rothschild Lord
Published: April 2021

The O2 uptake of Echinus esculentus sperm suspensions is strongly inhibited by CO. In equilibrium with a mixture of 90% CO and 10% O2, the O2 uptake is 60% less than that of an identical suspension in equilibrium with 90% N2 and 10% O2. This inhibition is completely reversed by light. Spectroscopic examination revealed cytochromes a, a3, b and c. On treatment with CO the spectrum of COa3 was observed. These results establish that the cytochrome system is the catalytic agent which controls the respiration of sea-urchin spermatozoa. The O2 uptake of sperm suspensions in equilibrium with 90% N2 and 10% O2 is about 10% lower than in air. Certain difficulties in measuring the R.Q. of sperm are discussed. The reversible effect of CO on the O2 uptake of spermatozoa is the same whether they are in egg water or sea water.
Anaphase Movements in the Living Cell
Authors: Hughes A. F. , Swann M. M.
Published: April 2021

The anaphase movements of living embryonic cells of the chick in tissue culture have been studied in phase contrast illumination, and in polarized light. Cine photographic records of chromosome movements and spindle changes have thereby been obtained simultaneously. Chromosome separation in the chick is made up of two components a movement of chromosomes towards the spindle poles, and an elongation of the spindle as a whole. The assumption is made that the force acting on a chromosome is directly proportional to the velocity with which the chromosome moves. If this assumption is accepted as an approximation, it is possible to interpret the relationship of chromosome velocity to chromosome separation and spindle-fibre length. This leads to the conclusion that anaphase movement is due, not to repulsion between chromosomes, but to a contractile mechanism operating from the spindle poles. Polarized light studies indicate that the orientation of the spindle material is high at the poles, and weaker at the equator. There is a small aster at either end of the spindle. The centrosomes are interpreted as centres of an orienting force, which build up the contractile mechanism of the spindle from isotropic protoplasm. It is suggested that asters may also be contractile, and cause elongation of the spindle. The inadequacy of the old conception of spindle fibres is discussed in the light of more modern views on molecular behaviour.
Laboratory Studies on the Egg of the Blowfly Lucilia Sericata (Mg.)
Authors: Davies Lewis
Published: April 2021

The chorion of the Lucilia sericata egg is shown to be composed of two main layers, both of protein ; the outer can be tanned by p-benzoquinone, but the inner is apparently already tanned. The chorion and the chorionic vitelline membrane are both lipidized shortly before the egg is laid. This makes both structures more rigid, but does not waterproof the shell. After the lipidization process is completed, a lipoid waterproofing layer is laid down by the öocyte, between the chorion and the chorionic vitelline membrane. This waterproofing layer has a critical temperature in the region of 38 ° C., and can be damaged by an abrasive dust, emulsified by the detergent I.C.I. C09993, and removed by chloroform at 30 ° C. in 12 hr.

The minimum humidity for development of L. sericata eggs at 37 ° C. has been found to be 50 % R.H. At 1 − 2 ° C. above this temperature eggs require about 80 % R.H. to complete development. Eggs at 37° C. can withstand fairly long periods of humidities below 50 % R.H., provided they have not been previously incubated in saturated air at that temperature. The latter treatment, even if continued for only 30 min., makes eggs far more susceptible to desiccation when subsequently incubated at a low humidity.

Fully developed larvae can survive imprisonment within the egg-shell for about 3 hr. at 37 ° C.
Observations on the Development of Lucilia Sericata (Mg.) Eggs in Sheep Fleeces
Authors: Davies Lewis
Published: April 2021

Comparative determinations of fleece atmosphere R.H. using cobalt-chloride papers and paper hygrometers showed that the former were reliable, although their use was subject to a limited humidity range (40−70 % R.y.). Determinations made by means of wool samples were found to be subject to large positive errors, since the wool near the skin did not appear to be in equilibrium with the fleece atmosphere. Measurements of fleece R.H. by cobalt-chloride papers on twenty-eight sheep of various breeds showed that the R.H. varied considerably from day to day in individual sheep, and in different sheep at the same time. The common condition was one of low R.H., unsuitable for the development of blowfly eggs. R.H. measurements and a study of the fate of L. sericata egg batches placed in fleeces showed, however, that conditions suitable for development were occasionally experienced in these sheep. Humidities high enough for hatching were more rarely found. Rapid secretion of watery material by the skin (sweating), leading to suitable humidity conditions for strike, was detected. The various sheep used showed great differences in sweating rates, the most rapid sweating being found in two Down Cross lambs where, at one period, the limiting factor for strike must have been that the blowflies were not attracted to them.
Studies in the Respiration of Paramecium Caudatum
Authors: Humphrey Beverley A. , Humphrey George F.
Published: April 2021

The lack of specific enzyme studies on protozoan material may be attributed mainly to manipulative difficulties. Burge & Williams (1927), in their substrate-utilization study on Paramecium caudatum, stated the position as follows: ‘The most difficult part of this investigation was the raising of these organisms in sufficiently large quantities and in fairly pure cultures.’ The slow advance of our knowledge of the nutrition of most types of Protozoa has left the position substantially unaltered. A few cultures of Protozoa on defined medium in the absence of other living organisms have been established (Doyle, 1943). Notably Chilomonas (Mast, Pace & Mast, 1936; Hutchens, 1939) and Tetrahymena (Kidder & Dewey, 1945) have been grown in a culture suitable for metabolic studies; many types have not been cultured free from their living food organisms, e.g. Amoeba and Spirostomum, and the bacteria-free culture of Paramecium of Johnson & Baker (1942) has a division rate so low as to render its use in metabolic studies impracticable.
The Absorption of Volatile Fatty Acids from the Rumen
Authors: Gray F. V.
Published: April 2021

In a previous paper the relative rates of absorption of acetic acid and propionic acid through the rumen wall were discussed (Gray, 1947a). While the manuscript was being prepared, Danielli, Hitchcock, Marshall & Phillipson (1945) described a series of experiments from which it was evident that the lower homologues of the fatty acids are absorbed through the rumen wall at different rates when the rumen contents are acid, and that the relative velocities of absorption fall in the series butyric > propionic > acetic. The observations made in this laboratory (Gray, 1947 a) independently and by different methods were in agreement with these conclusions. There is therefore no reason to doubt that the higher homologues are absorbed preferentially when the rumen contents are acid.
The Experimental Induction of Prenatal Mortality and the Subsequent Elimination of the Dead Embryos in Rabbits
Authors: Rogers Brambell F. W. , Henderson Megan , Mills Ivor H.
Published: April 2021

All the embryos in utero in pregnant rabbits were killed in a few hours by 5 mg. of stilboestrol administered subcutaneously. Experiments were performed on fourteen animals at 11 days, twelve animals at 1534 days and three animals at 19–20 days post-coitum. Embryos killed with stilboestrol administered at 11 or 1534 days post-coitum were invariably reabsorbed. Abortion occurred when the embryos were killed by stilboestrol at 19–20 days. Some or all of the embryos were killed in sixteen animals at 16 days and in five animals at 19–20 days post-coitum by perforating the uterus, membranes and embryos with a needle at laparotomy. Many of the embryos survived this treatment. Abortion occurs as a rule, but not invariably, when all the embryos are killed by surgical means. In the 16-day-series abortion is probably preceded by an initial period of autolysis. In the 20-day-series one animal reabsorbed but the others aborted. Destruction of some only of the embryos at 16 or 20 days post-coitum by surgical means usually results in reabsorption of the dead embryos and the maintenance of pregnancy, but may result in abortion. The occurrence of abortion may depend on the stage of development attained by the placenta. Abortion occurred at 1912-25 days post-coitum. There was no evidence that abortion occurred before the 19th day. The speed at which reabsorption proceeds varies with the stage of development of the embryos at the time of death, the manner of death, and whether some or all the embryos die. Reabsorption proceeds much more quickly after stilboestrol administration than after surgical interference. The dead embryos are much more persistent when others survive and the mother remains pregnant than when all are killed surgically. It is uncertain whether the greater rapidity of removal, when all embryos die, is due to more rapid autolysis or is due to the curtailment of reabsorption by abortion.
The Activity of Ram Spermatozoa
Authors: Rothschild Lord
Published: April 2021

Concentrated suspensions of active ram spermatozoa exhibit periodic changes in their electrical properties when these are measured in an a.c. bridge. Suspensions containing immobile or feebly active spermatozoa do not exhibit this phenomenon. The frequency of the changes has the following characteristics:It is maximal when the suspension is fresh, and declines to zero after some 60 min. at 37°C.It can be maintained for about 20 min. at a high level by the addition of phosphate buffer.It is susceptible to changes in temperature, the Q10 between 16 and 36°C. being about 2. A tentative hypothesis is put forward that these electrical changes are caused by the spontaneous, reversible aggregation, or ‘turbulent wave formation’, which is characteristic of active and concentrated suspensions of ram spermatozoa; and that they are due to the position of the spermatozoa in the measuring apparatus rather than to any intrinsic changes in the electrical properties of individual spermatozoa. As the frequency and intensity of the wave formations are thought to be proportional to sperm motility, there is a possibility that the electrical changes might be used as an objective and physical measure of sperm motility. Certain advantages and disadvantages in measuring the activity of the sperm suspensions by this method are discussed.
The Toxic Action of Copper and Mercury Salts Both Separately and When Mixed on the Harpacticid Copepod, Nitocra Spinipes (Boeck)
Authors: Barnes H. , Stanbury F. A.
Published: April 2021

The results are given of the poisoning of Nitocra spinipes (Boeck) by copper and mercury salts used together and separately. The state of copper and mercuric salts in sea water is examined using the available physico-chemical data. The results suggest that the two poisons act in a different manner and possible reasons for this are considered. The striking synergic effects obtained when the two metals are used together are considered to support the suggestion in 3 above and various possible explanations, both biological and chemical for this synergism, are examined.
Endocrine Activity During Insect Embryogenesis. Function of the Ventral Head Glands in Locust Embryos (Locustana Pardalina and Locusta Migratoria, Orthoptera)
Authors: Jones Bryn M.
Published: April 2021

A brain-ventral head gland system operates in embryos of Locustana pardalina and Locusta migratoria. The initiation of growth and differentiation on the termination of diapause in the egg of pardalina takes place before the ventral head glands are formed. Maximal activity in the ventral head glands coincides with the retraction of the epidermis from the cuticle. Embryos, dissected out of the egg, were kept alive in aerated sterile Ringer’s solution for up to 2 weeks during which time they progressed in their development. If post-katatrepsis embryos are ligatured between the thorax and abdomen before a * critical ‘period the moult is limited to the thorax. If ligatured immediately behind the head, the body fails to moult. Since on the termination of diapause in the egg of pardalina mitosis begins before the formation of the ventral head glands, it is suggested that in locust embryos these glands are exclusively concerned with the retraction of the epidermis from the cuticle. It is suggested that the uptake of water by the egg of pardalina in stretching the cells stimulates a growth factor which, although present throughout the diapause phase, is only capable of initiating mitosis after the diapause phase has come to an end.
Hormonal Control of Ovary Development in Mosquitoes
Authors: Clements A. N.
Published: April 2021

The control of ovary development by hormones has been shown in a number of insects, and evidence has been brought forward to demonstrate it in mosquitoes. It has been claimed on experimental grounds that a gonadotrophic hormone is secreted by the corpora allata after the intake of blood by female mosquitoes, co-ordinating ovary development with the supply of food (Detinova, 1945), and histological evidence has been produced connecting the corpora allata with ovary development (Mednikova, 1952).
Factors Controlling the Diurnal Rhythm of Activity of Periplaneta Americana L.
Authors: Harker Janet E.
Published: April 2021

By using a direct method of recording activity the diurnal rhythm of activity of Periplaneta americana L. has been investigated in detail under various conditions of light and darkness. It has been found that there is no direct connexion between a hunger cycle and the activity rhythm. By means of experiments in which cockroaches were joined together in parabiosis it has been shown that a rhythm can be relayed from one insect to another, and is postulated that a secretion carried in either the blood or tissues is responsible for the transmission. Implantation of sub-oesophageal ganglia from cockroaches with a known rhythm into headless cockroaches has been found to result in the appearance of the known rhythm of activity in the latter. Effects of other endocrine organs on the activity rhythm has been investigated. The ocelli have been found to be directly connected with the establishment of the rhythm by the external factors of light and darkness. A rhythm of activity subsidiary to the main diurnal rhythm is described.
The Osmoregulatory Ability of the Lampern (Lampetra Fluviatilis L.) in Sea Water During the Course of Its Spawning Migration
Authors: Morris R.
Published: April 2021

Although fresh-run lampems are able to withstand the effects of increasing sea-water concentration better than maturing animals, they can only maintain their plasma chloride constant in environments more dilute than 50 % sea water. This is achieved, in part, by gradually reducing the urine output from the normal fresh-water level (155-8 ml./kg./day) to a negligible rate in solutions which are mildly hypertonic to the blood (33 % sea water). Studies on the rate of change of weight loss, of plasma chloride and of plasma osmotic pressure following abrupt immersion in dilute sea water show that mature lampems cannot osmoregulate and can only survive in 33 % sea water by tolerating a raised blood osmotic pressure caused by water loss. Similar experiments on fresh-run animals suggest that the external surfaces of their bodies are less permeable to water than mature animals. Unlike mature animals, they also show considerable variation in the way in which they respond to 33 % sea water. Some are able to maintain their plasma osmotic pressure and chloride well below that of the environment. These animals also show little loss in weight, and this indicates that water is taken up actively, since this process has been shown to occur in some animals. Other fresh-run animals show raised plasma osmotic pressures in varying degrees and these are associated with larger losses of weight. These facts suggest that the hypotonic regulating mechanism gradually degenerates as the lampem enters fresh water.
Red Blood-Cell Antigens in Some Lower Vertebrates
Authors: Ashhurst Doreen E.
Published: April 2021

It was not possible to find evidence for blood groups in frogs (one species) or in fish (three species). Frogs could not be induced to make antibodies after injection with red cells from another frog. Frogs, toads and tree frogs have a B antigen; newts probably have not.
Studies On the Respiration of Sea-Urchin Spermatozoa
Authors: Mohri Hideo
Published: April 2021

Humphrey (1950) has established by microspectroscopic examination the existence of cytochrome spectra in oyster spermatozoa, and has further shown that cytochrome inhibitors such as cyanide and azide suppress the oxygen uptake of these spermatozoa. In sea-urchin spermatozoa, however, Barron, Nelson & Ardao (19486) have reported a contradictory result that, though the respiration is markedly depressed by cyanide, it is completely resistant to azide, even at high concentrations. On the other hand, Utida & Nanao (1954) have reported that the normal respiration of sea-urchin sperm is not affected by sodium azide, whereas the augmented respiration caused by 2,4-dinitrophenol (DNP) is completely abolished by this inhibitor. Since the presence of the cytochrome system in sperm cells has repeatedly been confirmed in a number of animals including sea urchins (Ball & Meyerhof, 1940; Zittle & Zitin, 1942; Mann, 1945; Rothschild, 1948), it is curious that azide fails to inhibit the normal respiration of sea-urchin spermatozoa.
Electricial Activity in A Slug Ganglion in Relation to the Concentration of Locke Solution
Authors: Hughes G. M. , Kerkut G. A.
Published: April 2021

In studies of the activity of isolated organs it is desirable to bathe them in a fluid similar to that found in the intact animal. Previous work on nervous systems indicates that their electrical activity is greatly affected by the concentration of ions in the medium, except in cases where they are enclosed in a thick impermeable sheath. In gastropods the suitability of a 0·6-0·75 Locke solution for in vitro experiments on isolated organs was demonstrated by Cardot (1921), who studied the effect of different dilutions of mammalian Locke solution on the frequency and amplitude of the heart beat in Helix. A 0·7 dilution (sometimes called Cardot’s solution) has generally been used by previous workers on the nervous system of gastropods, and their preparations retained constant electrical activity for many hours, but there is an absence of studies on the effect of variations in the composition of the bathing fluid on the gastropod nervous system. This is of interest because the blood of slugs and snails is known to show considerable fluctuations in concentration. The problem may also be of significance in relation to the general behaviour of the animal, since it is known that these fluctuations are related to the activity of the animals.
Reproduction and Growth of Mice of Three Strains, After Transfer to −3°C
Authors: Barnett S. A. , Manly Brenda M.
Published: April 2021

‘Wild’ house mice (Mus musculus L.) breed in cold stores kept at about–10° C (Laurie, 1946), and laboratory mice of the same species can be bred at an environmental temperature of–3° C., given nesting material (Barnett & Manly, 1954; Barnett, 1956). The response of mice to low temperatures varies with different inbred strains. The differences are reflected in mortality (especially of young), growth, numbers of young born and weaned, and in internal, especially endocrine, changes. All these, and other aspects of the maintenance of the lives of mice at low temperatures, are to be discussed in future communications.
Activation of Eggs by Hypothermia in Rats and Hamsters
Authors: Austin C. R.
Published: April 2021

Hamster eggs appear unique among known mammalian eggs in that nearly 80% were found to undergo spontaneous activation, extruding the second polar body, within 24 hr. of ovulation. Often the eggs showed spontaneous early parthenogenesis the development of one or occasionally two nuclei and the formation of a haploid first cleavage spindle took place in a manner that closely resembled the corresponding stages in fertilization. Time relations, too, were much the same. Rarely, however, does the cleavage spindle pass into mitosis, but instead it breaks up and the chromosomes become scattered. Only one normal-looking 2-cell egg was found.

Rat and hamster eggs were very resistant to activation by hypothermia while still in the ovary. After ovulation, however, 100% of rat eggs were activated by body temperatures between 0 and 1° C. and about 60-70% of hamster eggs by temperatures between 0 and 16° C. In view of the high incidence of spontaneous activation in hamster eggs, the effect of chilling in this animal can be regarded as merely that of hastening the change.

Hypoxia alone activated 36% of rat eggs. Relative tissue anoxia is therefore probably the immediate effective agent in activation by anaesthetics and is partly responsible for activation by low temperatures. Cold-shock itself, however, is evidently a more potent activator. Hamster eggs were not activated by hypoxia, probably because a less severe tissue anoxia was induced.

Rat eggs activated by hypothermia showed less tendency to early parthenogenesis than those activated by local chilling of the Fallopian tube.

Nucleus and spindle formation was rather better in artificially than in spontaneously activated hamster eggs, but the prospects of extensive parthenogenetic development did not seem in any way improved. Only two 2-cell eggs resembling fertilized eggs were seen.

Nuclei in activated hamster eggs achieved a volume similar to that of male or female pronuclei at full development. Total nucleolar volume was equal to the sum of the nucleolar volumes of male and female pronuclei.
Early Reactions of the Rodent Egg to Spermatozoon Penetration
Authors: Austin C. R. , Braden A. W. H.
Published: April 2021

In the rat, mouse and hamster the spermatozoon passes rapidly through the thick, homogeneous zona pellucida surrounding the egg and the head almost immediately becomes attached to the surface of the inner cytoplasmic mass or vitellus. As a result of this attachment a block to polyspermy is developed in rat and mouse eggs. In the hamster a block is apparently not formed. It seems likely, therefore, that the disappearance of cortical granules in the hamster egg, also an outcome of contact with the spermatozoon head, could signal the release of an agent that is responsible, after crossing the perivitelline space, for bringing about the zona reaction, reducing the penetrability of the zona pellucida to spermatozoa. Data suggest that this mechanism exists also in rats and mice, although a cortical granule response has not been distinguished in these animals. Thus, attachment of the spermatozoon head to the vitellus probably elicits both the zona reaction and the block to polyspermy.

These changes appear to be specific to spermatozoon penetration and to be initiated before the spermatozoon head passes through the surface of the vitellus and before the resumption of the second meiosis.
Acrasin, the Chemotactic Agent in Cellular Slime Moulds
Authors: Shaffer B. M.
Published: April 2021

A study has been made of acrasin, the agent inducing chemotaxis in the amoebae of cellular slime moulds. A method has been developed for subjecting sensitive amoebae to a fluctuating gradient set up by an artificial source that can be renewed at intervals of as little as a few seconds with fresh test solution. Amoebae orient to a gradient maintained with the cell-free liquid freshly obtained from the immediate surroundings of a natural source. Acrasin solution as secreted loses its activity very rapidly at room temperature. A highly active stable solid is obtained by drying methanolic culture extracts ; it resists boiling and exposure to acids and alkalis. Its solubility decreases rapidly in passing up the alcohol series. The original instability has been shown to be due to the presence of another extracellular slime-mould product, possibly an enzyme; it, unlike acrasin, cannot pass rapidly across a dialysis membrane, is heat labile, and can be precipitated by ammonium sulphate. The advantages of the organism’s itself inactivating acrasin are considered. Some of the advantages of a source’s releasing acrasin in pulses are discussed ; but it is not essential for orientation for it to do so. Sensitive amoebae not only are oriented by an acrasin solution but are caused to secrete acrasin: this is the basis of a chemotactic relay system.
Tetanic Force and Shortening in Locust Flight Muscle
Authors: Weis-Fogh Torkel
Published: April 2021

The maximum tetanic force and shortening was studied in the isolated, dorsal-longitudinal muscle of the hindwings of the desert locust (Schistocerca gregaria). The muscle tended to die when isolated in artificial salines but after penicillin had been added it survived well for more than 8 hr. at 32° C. The cause is discussed. The flight muscle is very sensitive to lack of oxygen and, at room temperature and above, it is necessary to perfuse the main tracheae with air. No difference was observed between indirect and direct stimulation. The natural activity consists of repetitive twitches. Tetanic contractions always caused rapid fatigue and tended to injure the muscle, partly because of excessive shortening (‘delta state’) and partly because the muscle ‘gave’ at the comparatively small total tension of 2-2·5 kg.cm.-2. The length-force diagram at 11° C. resembles that of ordinary skeletal muscle, but the maximum shortening (o-45L6) and the maximum isometric tension (1·6 kg.cm.-2) are smaller than in frog muscle at that temperature. As in mammahan muscle, the isometric tension increases much with temperature and was estimated indirectly as 3 kg.cm.-2 at 25° C. and 4 kg.cm.-2 at 35° C. The largest observed shortening was 0·55Lb. At ordinary body temperature, tension and work are of the’ same magnitude as in skeletal muscle of vertebrates. The flight muscle is less extensible than frog muscle and the maximum isometric force is produced at a lower I-band/sarcomere ratio (0-2). As in frog muscle, passive stretch only affects the I-bands, while the A-bands remain at constant length, at least in the fixed material used here. It is probable that the mechanical specialization of the flight muscle mainly concerns the sarcolemma and the other passive-elastic elements; the contractile elements do not seem to differ from ordinary muscle.
An Inexpensive Type of Sound-Proof Room Suitable for Zoological Research
Authors: Thorpe W. H. , Hinde R. A.
Published: April 2021

The design of an inexpensive sound-proof room, virtually sound-proof to audiofrequencies of 2 kc. and above, is described. Since for the purposes of many zoological experiments low frequencies can safely be disregarded, it is felt that on account of cheapness and relative ease of construction, this type of sound-proof room has much to recommend it.
Hearing in Certain Orthoptera
Authors: Haskell P. T.
Published: April 2021

The physiology of sound reception by tympanal organs, long hair sensillae on the anal cerci, and hair sensillae on the thorax and abdomen has been studied by electrophysiological methods in four species of Acrididae, namely Stenobothrus lineatus, Omocestus viridulis, Chorthippus parallelus and C. brunneus. The discharge in the tympanal nerve of all four species on stimulation by pure tones was asynchronous and showed no equilibration or fatigue. Comparative data are given for threshold sensitivity to pure tones for the four species over the range 0-20 kc./s., and shows the sensitivity to be very similar throughout the group. The tympanal organs of all four species responded to pulsed sound with synchronous volleys of spikes up to pulse repetition frequencies between 90 and 100 pulses per second ; at higher rates synchronism broke down. Long-hair sensillae on the anal cerci responded to gross air movements with bursts of spikes and to pure tones up to 300 c./s. with a synchronous discharge. The cereal nerves synapse with fibres in the ventral nerve cord, and the postganglionic discharges on continuous maximal stimulation of the cereal sensillae show accommodation. It is concluded that these cereal sensillae are similar in response and innervation to those on the cerci of the cricket, cockroach and migratory locust, but that owing to their small number and restricted frequency range they are probably not concerned with reception of natural stridulation. Discharges were evoked in segmental nerves of the third thoracic ganglion in the four species in response to vibration of the substratum and stimulation by airborne sounds. The sensillae mediating the vibration response are hair sensillae situated on the abdominal stenites. The receptors mediating response to air-borne stimuli may be hair sensillae on the abdominal pleura and stenites, or segmental chordotonal sensillae. The present work indicates that the former are probably the receptors concerned, but further work to elucidate the roles played by the two types of organ is required. Data are given on the response and threshold of the hair organs. The responses of all the sound receptors investigated were independent of age and sex and also, in females, of the state of the ovaries.
Hearing in Certain Orthoptera
Authors: Haskell P. T.
Published: April 2021

The pattern of nervous discharge from tympanal organs and abdominal hair sensillae resulting from stimulation by natural and imitation stridulation has been studied in four species of Acrididae, namely Stenobothrus lineatus, Omocestus viridulus, Chorthippus parallelus and C. brunneus. Experiments with tympanal organs stimulated repeatedly with identical sound pulses show that the resultant volleys of spikes, although synchronous with the pulse frequency of the stimulus, were variable in themselves, and that this variability was random, bearing no simple relationship to any quality of the stimulus. This variability in the structure of the impulse bursts was manifested with both natural and imitation stridulation. The response of abdominal hair sensillae showed them to be capable of signalling the duration of supra-liminal stimuli, and responses signalling pulse repetition frequencies were limited to cases where the pulse rates did not exceed 5 per second. In the present species, this meant that only the normal songs of C. brunneus and C. parallelus would produce impulse bursts in tergal nerves synchronous with the pulse frequency of the stimulus. On the basis of this evidence it is adduced that the characteristic of stridulation which enables inter-specific recognition to be effected is the pulse repetition rate of the songs. Comparative data from the four species show that the auditory receptors throughout are very similar, and thus the pattern of nervous discharge will be, in its essential element of the rate of impulse burst, the same for all species when exposed to the same stimulus. The discrimination process must thus be a central one, and it is suggested that this problem might be examined in relation to the ‘Reafferenzprincip’ of von Holst & Mittelstaedt (1950).
A Study of Ovarial Development and Its Relation to Adult Nutrition in the Blowfly Protophormia Terrae-Novae (R.D.)
Authors: Harlow Phyllis M.
Published: April 2021

A method has been developed for obtaining 200-300 flies daily from a culture of Protophormia terrae-novae reared on whale-meat. Normal growth changes in adults have been described, and five stages in ovarial development have been defined. Experimental conditions affecting ovarial growth in adults have been investigated and a satisfactory routine method for examining the effect of adult nutrition on ovarial growth has been devised. Precautions were taken against bacterial contamination of food although non-sterile conditions were used. Ovarial development was not related to relative humidity, if above 55 % R.H., nor to the weight of the adults at emergence. Evidence has been given for the conversion of food material from pupal to adult fat body and for the transfer of material from fat body to ovaries at yolk formation. Healthy adult females can be maintained on a diet of sucrose and water. Addition to the diet of protein or amino-acids produces only slight enlargement of the ovaries. Yolk formation only occurs if the diet is further supplemented by accessory factors, or substances required only in small amount. Ovarial maturation requires considerable amounts of protein, though not more than 0-4 mg. per fly is needed and food solutions must be concentrated. The accessory factors have not been identified but are known to be resistant to slow boiling and are dialysable. Certain mineral salts and B vitamins are thought to be involved. Tryptophane is an essential part of the amino-acid mixture. Protein hydrolysates or equivalent amino-acid mixtures can be substituted for the whole protein but are less effective. The proportions of amino-acids present are very critical, particularly when the amino-acids are in a free state. The aminoacid mixtures have no toxic effect and the presence of some D-isomers do not inhibit growth, although some D-isomers cannot be used by the flies for growth. A chemically defined diet similar to that used for Drosophila did not promote ovarial growth in Protophormia. A mixture containing ten B vitamins, ribose nucleic acid and mineral salts and cholesterol contained some effective accessory substances but lacked some unidentified factor required for yolk formation. The missing factor was not vitamin B12. Penicillin had no significant effect on ovarial growth whether used in minute or in antibiotic concentration.
The thermal sensitivity of the lateralis organs of Xenopus
Authors: Murray R. W.
Published: April 2021

A convenient isolated preparation of the lateralis organs and nerve of Xenopus laevis is described. An average of two active units can be obtained by cutting between the groups of organs in the skin. There is a basic discharge, which is irregular and which varies directly with steady temperatures. An opposite response is obtained to temperature changes. On cooling there is an increase in frequency adapting to the new steady level with a time-constant of 20 sec., and on warming there is a corresponding decrease in frequency. The threshold for temperature change is 1-2° C., representing a rate of change of temperature of ο⋅3-ο⋅6° C./sec. at the surface of the skin. In the more sensitive preparations the basic frequency is doubled or com­pletely inhibited by a change of 5° C. The threshold change of temperature for similar preparations of skin and segmental cutaneous nerve is 5-10° C. The discharge frequency can be increased by mechanical stimulation, but only at intensities high enough to act at the nerve endings directly and not by way of the sensory cells. The sensitivity is comparable to that of the segmental cutaneous nerves.
Absorption of Water by the Egg of the Garden Chafer, Phyllopertha Horticola L
Authors: Laughlin Roger
Published: April 2021

Many insect eggs absorb water during the incubation period. Buxton (1932), Roonwal (1936) and Matthée (1951) review the numerous reports published since 1740 when Réaumur noticed that eggs of sawflies and ants increased in size during development.
Effects of High Hydrostatic Pressures on Actinophrys Sol (Heliozoa)
Authors: Kitching J. A.
Published: April 2021

The axopods of Actinophrys sol are caused to collapse by the application of high hydrostatic pressures. Axopods grow out again on release of pressure or on reduction of pressure below a certain critical value. Temperature and pressure act in opposition as regards the outgrowth and maintenance of axopods. At 15° C., the average critical value for the restoration of axopods is about 3500 p.s.i. (207 atm.). An increase of temperature by ro° C. counteracts an increase in pressure of 1200 p.s.i. (82 atm.).
Transplantation of Melanomas from Platyfish-Swordtail Hybrids Into Embryos of Swordtails, Platyfish and Their Hybrids
Authors: Humm Douglas G. , Clark Eloise E. , Humm Jane H.
Published: April 2021

The melanomas in the platyfish–swordtail hybrid are produced genetically, as shown by Gordon (1951), by the interaction between the macromelanophore growth-modifying factors from the swordtail and a dominant platyfish sex-linked allele controlling the appearance and distribution of macromelanophores. The genic interaction manifests itself phenotypically in that the macromelanophores appear in the hybrid much earlier than in the normal platyfish and the growth of the pigmented cells seems relatively unchecked, resulting in hyperpigmentation of the animal and ultimately in the production of a tumour. (See Reed & Gordon (1931) and Gordon & Smith (1938) for a detailed description of the phases of tumour development.)
An Apparatus for the Study of the Locomotion of Fish
Authors: Bainbridge Richard , Brown R. H. J.
Published: April 2021

In studies on the swimming of fish using the small ‘fish wheel’ (Bainbridge, 1958) it became clear that to enable the research on swimming speeds to be extended to larger specimens and to give scope for the investigation of other problems, a larger apparatus was needed. With the generous support of Messrs Watts, Watts and Company Ltd., The British Steamship Company Ltd., and the British Thomson-Houston Company Ltd., the development of this large wheel became possible. The construction of the wheel itself was undertaken in the Zoological Department, Cambridge, while the electric drive was supplied by the British Thomson-Houston Company.
Embryonic Mortality in Relation to Ovulation Rate in the House Mouse
Authors: Bowman J. C. , Roberts R. C.
Published: April 2021

Two series of observations were made to determine the time and amount of loss of eggs in relation to the number shed per ovary and per mouse. The correlations between sides within mice for eggs shed was −0·528, for corpora lutea counts −0·436, for implantations −0·300, and for live embryos −0·111. A positive linear trend of loss of fertilized eggs with increasing numbers of eggs per uterine horn has been shown to occur before implantation. Possible causative mechanisms for the loss are discussed in relation to observations on embryonic mortality previously reported by other workers. We wish to express our gratitude to Prof. C. H. Waddington for laboratory facilities, to Dr D. S. Falconer for much helpful criticism and advice and to Dr B. Woolf for statistical advice. J. C. Bowman gratefully acknowledges financial support from the Agricultural Research Council.
Chemotaxis of Bracken Spermatozoids
Authors: Brokaw C. J.
Published: April 2021

Fern spermatozoids respond chemotactically to concentration gradients of malic or maleic acid salts (Pfeffer, 1884). They respond weakly to salts of a few other dicarboxylic acids, but do not respond to succinate or fumarate (Shibata, 1911; Rothschild, 1956). Previous workers concluded, without adequate justification, that the malate ion, and not the undissociated malic acid molecule, is chemotactically active; but no consideration has been given to the possibility that the bimalate ion may be the active species.
Effect of the Black Snake Toxin on the Gastrocnemius-Sciatic Preparation
Authors: Mohamed A. H. , Zaki O.
Published: April 2021

When the toxin of the black snake (Walterinnesia aegyptea) was injected subcutaneously into albino rats, one of the common symptoms which appeared was the paralysis which takes place in the limb near the site of injection and extends to other limbs just before death.