bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Fertilization Reaction in the Sea-Urchin
Authors: Rothschild Lord , Swann M. M. 
Published: April 2021

ABSTRACT
The reactions of sea-urchin eggs (Psammechinus miliaris) to high concentrations of homologous spermatozoa have been investigated by a new method. The method was to inseminate eggs with high concentrations of spermatozoa (108/ml.), which ensured that all eggs were fertilized for the first time at the beginning of the experiment; and then functionally to separate the eggs and spermatozoa at known times after the original insemination. The proportion of polyspermie eggs in the suspension rises from zero at t = 0 to a constant value at a time T, which is the conduction time of the block to polyspermy. In fourteen experiments on eggs from different sea-urchins, the estimated values of T were 17, 69, 72, 74, 94, 85, 26, 60, 31, 91, 85, 34, 75 and 67 sec. (arithmetic mean 63 sec.). The standard errors of the estimates of T, which are tabulated in the text, ranged from 5 to 15 sec. These results confirm previous experiments which strongly suggested that the conduction time of the block to polyspermy was of the order of seconds; these earlier experiments were incompatible with a block to polyspermy lasting a fraction of a second. At the same time experiments in this paper made it possible to estimate the fertilization parameter or sperm-egg interaction rate a, during the conduction of the block to polyspermy, and to compare it with the pre-fertilization a. In a given sperm suspension, a is a measure of the receptivity of the egg surface to spermatozoa. During the conduction of the block to polyspermy a was found to be markedly lower (1/20) than in unfertilized eggs. This suggests that at fertilization there is a fast but incomplete block to polyspermy, whose conduction time may be 1 sec. or less. This is followed by the slower block which finally makes the egg impermeable to spermatozoa. This also confirms previous observations on the small incidence of polyspermy at normal sperm densities, which is not consistent with the concept of a slow block to polyspermy.
The Effect of Type of Contact with the Organizer on the Nature of the Resulting Induction
Authors: Waddington C. H. , Deuchar E. M. 
Published: April 2021

ABSTRACT
The result of the activity of the primary organization centre in the amphibian gastrula is to determine a complex organized pattern of development. Within the ectoderm there arises a neural system in which, at the early stages, one can distinguish at least three different developmental types—brain, neural tube and neural crest ; another part of the animal hemisphere becomes mesoderm, and this can also be the result of an inductive action, since transplanted presumptive ectoderm can be caused to develop in this manner. There is general agreement that one cannot attribute these different end-results to any great extent to differences in the competence of the ectoderm submitted to the induction. There therefore remain two other factors to be investigated: differences either of a quantitative or qualitative nature within the organization centre, and differences in the type of contact between the various regions of the animal hemisphere and the organizer by which it becomes underlain. Waddington & Yao (1950) pointed out that there must be differences within the mesoderm in the rate at which evocating power is developed and in its final intensity, and they drew particular attention to the possible importance of the varying lengths of time during which the more anterior and the more posterior parts of the future neural system are in contact with inducing material.
The Random Element in Bird ‘Navigation’
Authors: Wilkinson D. H. 
Published: April 2021

ABSTRACT
An analysis is presented of the results to be expected from experiments on the homing of wild birds if the only factor operating is random search. It is found that this model reproduces the experimental results and predicts values for the parameters involved in the theory which are inherently plausible and which are in quantitative accord with experimental evidence. Attention is paid to the dependence of percentage return on distance of release, to the dependence of the average speed of return on this distance, and to the distribution in time of the returns. These three sets of data form a coherent picture within the framework of the hypothesis of random search. Certain types of migration are also briefly considered.
It is not suggested that this investigation proves that random search is indeed the mechanism by which the homing of wild birds is accomplished, but it is submitted that the large-scale experiments of the type considered here are not susceptible of the interpretation that a true navigational ability is involved.
Further Developments on the Dynamics of Ovarian Hypertrophy
Authors: Lipschütz Alexander , Voss H. E. V. 
Published: April 2021

ABSTRACT
It has been shown (Lipschütz, 1925) that the number of young ova in an hypertrophied ovarian fragment or in a fragment which has increased its volume by formation of cysts, is highly reduced as compared with a normal ovary. This phenomenon is of great significance for the understanding of the dynamics of ovarian hypertrophy. However this statement is not free from objections. If the diminution of young ova in such an ovarian fragment is really caused by the fact that a relatively greater number of young ova are used for follicular development, then there should be in certain cases an almost complete disappearance of young ova. Now there was only one case of a rabbit where this could be ascertained with surety (case B III.); but in this it was not known whether the fragments were not originally so small that the number of young ova was from the beginning a minimal one. As long as no case is available in which an almost complete disappearance of young ova in an increased ovarian fragment had been proved by counting the young ova in all the sections of that fragment, the objection is justified that the diminution of young ova is only an apparent one, the number of young ova originally present being now scattered in a greater volume. Moreover, the diminution of young ova might have been caused not by an increased follicular development but by some local conditions or by the operative interference.
Note On The Chromosomes Of The Genus Hypericum, With Special Reference to Chromosome Size in H. Calycinum
Authors: Chattaway M. M. 
Published: April 2021

ABSTRACT
With the exception of four isolated papers published at different times since 1911, the large group of the Guttiferales had been undescribed from a cytological standpoint, until the appearance in the autumn of 1924, in Hereditas, of a paper by Niels Neilsen upon “Chromosome numbers in the genus Hypericum.”
The Effect of Gonadectomy on the Weight of the Kidney, Thymus, and Spleen of Mice
Authors: Masui Kiyoshi , Tamura Yasusige 
Published: April 2021

ABSTRACTThere is a distinct sexual difference in the body weight of the mouse, the males being considerably heavier than the females. As the result of gonadectomy in the male there occurs no change in the body weight, while in the female it increases rapidly after spaying. A slight sexual difference is seen to exist in the body length, the females being longer than the males. Body length increases slightly after castration, while spaying produces no effect. There is a distinct sexual difference in the weight of the kidney, it being strikingly heavier in the male. The kidney of the castrated male becomes greatly reduced in weight and approaches that of the female kidney ; in the spayed female only a slight reduction in the weight of the kidney may be observed. The thymus of the female is considerably heavier than that of the male. As in the kidney, castration is followed by a striking increase in weight which approaches that of the female thymus ; spaying has but little effect. There is a distinct sexual difference in the weight of the spleen, it being considerably heavier in the female. The results of castration and of spaying are the same as in the case of the thymus. The results of the present study do not agree with Lipschütz’s hypothesis of an “asexual” type, for as the result of gonadectomy in the male the weight of the kidney, thymus, and spleen approaches that of these organs in the female, or, in other words, gonadectomy is followed by a development of the characters typical of the opposite sex.
Some Observations on the Dissociation of Hæmocyanin by the Colorimetric Method
Authors: Hogben Lancelot T. 
Published: April 2021

ABSTRACT
By means of the colorimetric method the effect of temperature, hydrogen ion concentration, and salinity upon the dissociation of the hæmocyanin of four species of decapod crustacea (Maia, Cancer, Palinurus, and Homarus) has been studied. Rise in temperature depresses the dissociation curve continuously between 0° and 50° C. Reasons are given in favour of the conclusion that this behaviour is consonant with the applicability of the mass action law. On this understanding the heat of reaction between hæmocyanin and oxygen dissolved in the water phase in the case of Maia is of the order 9500 calories per n gram molecules of oxygen, n being defined as the least number of molecules of oxygen which can enter into the reaction. In the case of all four crustaceans referred to above, the affinity for oxygen diminishes up to a point as the hydrogen ion concentration is increased: on further increasing the hydrogen ion concentration beyond a critical value for which the affinity of the serum for oxygen is minimal, the amount of oxygen taken up at low tensions increases and may surpass the values obtained for serum at normal pH. The similarity of this result with the observations of Rona and Ÿllpo on hæmoglobin is discussed. On concentrating serum with neutral chlorides of the alakali and alkaline earth metals the dissociation curve is made steeper.
The Effects of Fat-Soluble Vitamin A Deficiency on Reproduction in the Rat
Authors: Parkes A. S. , Drummond J. C. 
Published: April 2021

ABSTRACTIt is well known that vitamin A deficiency in the young animal checks growth and results in stunting for the period of the deficiency, Such animals, however, resume growth and reach the normal adult weight when put on to a complete diet. Animals in this dwarfed condition, weighing 70 to 90 gms. only at 3 to 5 months old, are quite sterile. Histological examination of the gonads and secondary organs, however, revealed in most cases no anatomical reason for their sterility. Gametogenesis was found to be in progress in these stunted animals, and the accessory organs appeared to be normal. It was concluded, therefore, that the sterility was due, primarily to physiological debility and disinclination to copulate. That this was actually the case was shown by a further batch of deficiency animals which were reciprocally mated with each other and with normals, daily examinations being made for evidence of copulation. None of the females copulated, but one only slightly deficient buck copulated with a normal doe. At the same time, however, vaginal smearing showed that the cyclic activity in the female genital organs, associated with the œstrous cycle, occurred in the deficient females. When normal weight is attained after recovery on natural diets breeding takes place freely, and fertility and sex-ratio show no marked abnormality.
On The Physiology of Amoeboid Movement
Authors: Pantin C. F. A. 
Published: April 2021

ABSTRACTContinuous amoeboid movement is essentially a rhythmic phenomenon (Pantin, 1924), to some extent comparable with rhythmic contraction in muscle. Yet no complete investigation of the action of ions has been made which enables this unspecialised contractile mechanism to be compared with heart-muscle and cilia. The subject is important because in unicellular organisms the state of the cell can be observed simultaneously with the movement; it can also be seen at once if all the cells react in the same way. In muscle only indirect evidence can be obtained on these points.Marine amoebae are peculiarly suitable for this work, because the composition of sea-water is accurately known and an artificial medium therefore prepared with comparative ease. Quantitative results are obtained by selecting a species of the limax type and measuring the rate of movement.
On The Physiology of Amoeboid Movement
Authors: Pantin C. F. A. 
Published: April 2021

ABSTRACTThe previous paper of this series (Pantin, 1926) described the action of certain ions upon a species of marine amoeba, and especially the relation of calcium to amoeboid movement. The same paper detailed the method of preparing isotonic salt solutions and of determining their effect on amoeboid movement. The essential feature is that the average velocity is taken as a measure of the effect of a solution upon the power of movement, apart from other effects produced upon the cell. Unless otherwise stated, the CH of the solutions was maintained at pH 7.0 to 7.2.
Simultaneous Determination of Sodium and Potassium in Small Volumes of Fluid by Flame Photometry
Authors: Ramsay J. A. , Brown R. H. J. , Falloon S. W. H. W. 
Published: April 2021

ABSTRACT
A method of flame photometry is described, by which the amount of sodium and potassium in biological fluids can be determined simultaneously, using samples of the order of 10−3 cu.mm. When the method is tested with quantities near the lower limits of detection (of the order 4 × 10−8 mg. sodium, 6 × 10−8 mg. potassium) the reproducibility, measured as standard deviation, is ±7 × 10−9 mg. sodium and ± 17 × 10−9 mg. potassium. When larger quantities (up to certain limits) are used, the standard deviation is approximately ± 3 % of the quantity in the sample, both for sodium and for potassium. As is usual in flame photometry serious errors can be caused by the presence of other substances in the sample. In the case studied for purposes of illustration it is shown that these interference errors can be reduced to the order of ± 6 % by the addition of excess ammonium phosphate.
The Fertilization Reaction in the Sea-Urchin
Authors: Rothschild Lord 
Published: April 2021

ABSTRACT
Treatment of unfertilized sea-urchin eggs with sea water containing nicotine is known to induce polyspermy when the eggs are subsequently inseminated with homologous spermatozoa, at densities which cause a very small amount of polyspermy in untreated eggs. If nicotine were to increase the speeds at which sea-urchin spermatozoa swim, the chances of fertilization, and therefore of polyspermy, might be increased. Nicotine does not increase sperm speeds; in addition, it causes a sharp reduction in the O2 uptake of these spermatozoa. The only other ways in which nicotine could induce polyspermy are by altering the egg surface in such a way that the probability of fertilization is increased by a factor of about twenty; or by lengthening the conduction time of the block to polyspermy. Experiments described in this paper show that the first explanation is untenable and therefore that the second is the correct one. It is concluded that nicotine abolishes the fast incomplete block to polyspermy and that over-exposure to this substance probably abolishes the block to polyspermy altogether. Polyspermic eggs divide sooner than monospermic ones. When, as in these experiments, eggs are allowed to interact with spermatozoa for known times, and then functionally separated by immersion in hypotonic sea water, some eggs, presumably those which sustain a successful sperm-egg collision at the end of the interaction time, are activated but not fertilized by the spermatozoon, as in the pseudogamous nematodes. Cleavage does not occur though the egg nucleus swells. Previous results in the same field and observations by other workers are discussed.
The Flight of Birds
Authors: Brown R. H. J. 
Published: April 2021

ABSTRACTIn a previous paper (Brown, 1948), the movements of the wing of a pigeon in slow flight were analysed. With the help of a new photographic technique further work on the flight movements at different forward velocities has been carried out. In this paper the analysis is extended with additional information obtained from normal cine-photography. Certain improvements and simplifications in the flash cinematographic methods are also described.
The Gregarious Behaviour of MarchingLocusta Migratoria Migratorioides(R. & F.) Hoppers
Authors: Ellis Peggy E. 
Published: April 2021

ABSTRACTThe amount of marching by 4th-instar hoppers of Locusta migratoria migratorioides (R. & F.) which have been reared in crowds, was studied in relation to the total number of individuals and to the size of the cage. Below 50 hoppers per cage, marching depended partly on the total number of hoppers present and partly on the number in relation to the area of the cage floor. Above 50 hoppers per cage, marching probably depended on the total number present, rather than the area of the cage floor. In all cages, marching was greatly reduced with fewer than 30 hoppers, although even single individuals marched for part of the time. An investigation of the hopper interactions which lead to an increase in marching activity in groups showed that the two most important were visual and mechanical ones. Test hoppers followed moving hopper bodies alive or dead, but only gave a partial response to moving vertical stripes. Mechanical interactions between hoppers greatly increased the proportion of reacting hoppers, but did not increase the distance travelled by the active individuals, beyond those travelled in response to optical stimuli alone. Maximal marching activity, by the maximal proportion of hoppers in a band, depended on an opto-motor response to a moving background of hopper shapes and to the physical contact between hoppers. Air and floor vibrations from other marching hoppers played only a small part in marching, whilst stimuli received via the antennae tended to inhibit marching when total activity was low. The importance of the experimental results in explaining the behaviour of locust hoppers in the field was discussed.
Sun Navigation in Homing Pigeons
Authors: Matthews G. V. T. 
Published: April 2021

ABSTRACTThe accumulated data of a long series of homing experiments carried out with young pigeons is examined in statistical detail. Bico-ordinate navigation can only be demonstrated in sunny conditions, and with overcast skies the birds scatter at random. This holds for a number of different experimental situations. The hypothesis that pigeons use a form of sun-navigation, deriving latitude and longitude from the sun position alone is re-examined in detail. None of the requirements are outside the theoretical range of the organ concerned, or beyond the bounds of possibility. Examination of the errors made under sunny conditions shows that their nature and variation are as expected on the basis of the hypothesis. So also is the variation in error with the length of time of observation. By excluding sun and sky for a number of days before release a re-orientation away from home was obtained. This could only be explained if the birds were failing to correct for the seasonal variation in the sun’s altitude, and deriving their latitude from altitude measurements. Radical changes in accustomed release times produced some increase in longitude errors. After treatment aimed at desynchronizing any internal chronometer a disorientation was obtained in the field. It is therefore very probable that longitude determination is on a time basis, as proposed in the hypothesis. Future lines of research in this problem are indicated.
The Orientation of Untrained Pigeons: a Dichotomy in the Homing Process
Authors: Matthews G. V. T. 
Published: April 2021

ABSTRACTIt is demonstrated that young pigeons without any previous training show a definite homeward orientation at a distance, yet home very badly. The results are compared with those of birds with varying amounts of training. An essential dichotomy in the homing process is revealed, between the orientation process which is innate and the process of return which is governed by factors developed by individual experience. The further contrast between the unitary nature of the orientation process and the multiplicity of factors concerned in the return is supported by statistical consideration of the individual variation in ability. The practical and theoretical implications of these conclusions are considered.
Navigation in the Manx Shearwater
Authors: Matthews G. V. T. 
Published: April 2021

ABSTRACTHoming experiments were carried out with 338 Manx Shearwaters from Skokholm Bird Observatory, Pembrokeshire. The especial advantages of this species for such work are described. With sunny conditions, strong homeward orientation was shown by birds released at points unknown to them. Early in the season these releases gave very fast, complete returns, more than half back on the first 2 nights. Those on the first night were unequivocal evidence of long, direct flights over unknown country. One shearwater homed at least 3050 miles across the Atlantic in 1212 days. There was a decline in the proportion of returns later in the season, probably due to a loss of stamina. With conditions of heavy cloud the homeward orientation broke down and returns were poorer. The stage of the individual incubation shift has some effect on the homing performance. For the first time we have a demonstration of complete evidence for navigational ability in a wild bird. The suggestion of a form of sun navigation is in line with evidence obtained with pigeons and gulls. The failure of workers with other species to produce such evidence is not considered to weigh against the possibility of navigational ability of this kind in all proven homers. The sun-navigation hypothesis is investigated. Although shearwaters fly to the burrows after dark they are unable to navigate after sundown. Determination of the latitude from the sun’s altitude can only be tested in this species by trans-equatorial experiments. Determination of longitude by time differences was tested by attempting to desynchronize the necessary internal ‘chronometers’. The first attempt was in-conclusive owing to cloudy conditions at release. A second attempt was also partially thwarted by the weather, but gave suggestive results favouring the hypothesis. More experiments of this nature are required. An analysis of the range of shearwaters from the colony, based on banding results, is given. The Wilkinson flight-duration recorder was used on this species, but did not give satisfactory results.
Studies on the Mesogloea of Coelenterates
Authors: Chapman Garth 
Published: April 2021

ABSTRACTThe physical properties of the isolated mesogloea of Calliactis and Metridium are described and the behaviour of the tissue on loading recorded. It can be compared with a spring and dashpot model. It is shown that the viscous-elastic properties of the body-wall, which have previously been ascribed to the muscles, are the attributes of the mesogloea. On being heated in water under a small load, isolated mesogloea of Calliactis contracts, at temperatures which are only a little higher than those at which vertebrate collagen contracts. This is regarded as additional evidence for the collagenous nature of the mesogloea protein. It is shown that the physical behaviour of the material is consonant with the crossed fibrillar collagenous nature of the mesogloea described elsewhere.