bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiographic Studies on the Formation of the Hen’s Egg Shell
Authors: Bradfield J. R. G. 
Published: April 2021

ABSTRACT
Radiographic methods have been used to study the rate of deposition of the hen’s egg shell and the changes in volume and orientation undergone by the egg in the shell gland. Shell deposition commences about 5 hr. after the yolk is ovulated and several series of radiographs were obtained tracing the process from these earliest stages through to the fully calcified shell. From radiographs of calcium carbonate-gelatin mixtures it was found that, for a series of comparable objects differing only in calcium carbonate content, the densitometer readings on their radiographs were directly proportional to the density of calcium carbonate traversed by the X-rays in each object. Hence, densitometer measurements on the periphery of the shell in each of a series of radiographs taken during the development of a single egg shell give values which are proportional to the density (or thickness) of calcium carbonate traversed by the tangential rays. It is shown that the radial thickness is closely proportional to the square of these values. Plotting these squared densitometer readings against time indicates that the rate of deposition of mineral matter in the shell follows an S-shaped curve, with a marked acceleration in shell deposition 5–6 hr. after its onset. During its first few hours in the shell gland, the egg undergoes a 25 % osmotic increase in volume. This swelling is brought to a fairly abrupt halt by the increase in the rate of shell deposition and the consequent increase in the impermeability and rigidity of the shell. Throughout all but the last hour or two of its 20 hr. stay in the shell gland, the egg lies with its pointed end caudal. Shortly before it is laid, however, it usually undergoes a 180° rotation in a horizontal plane. Thus the blunt end finally becomes caudal and emerges first when the egg is laid. During the rotation, the egg sinks to a more ventral position. This is necessary because, in most hens, the length of the egg plus the thickness of the walls of the shell gland is greater than the width of the pelvis. The possible significance of the S-shaped curve of shell deposition is discussed. The volume, shape and orientation of the egg are considered in relation to the needs of the chick embryo and to the characteristic structure of the bird’s oviduct and pelvis.
The Body Temperature of Woodlice
Authors: Edney E. B. 
Published: April 2021

ABSTRACT
Measurements by means of thermocouples, accurate to 0.1° C., were made of the body temperature of the woodlice Armadillidium, Porcellio, Oniscus and Ligia, and of the cockroach Blatta, both alive and dead, in a stream of saturated or dry air at both 20 and 37° C. No difference in temperature depression was found between living and dead woodlice, and in all the animals used there was, after equilibration, no difference greater than 0.1° C. between the air temperature and body temperature if the air were saturated with water vapour. In dry air, the body temperature of all the animals except Ligia settled down after at most 25 min. to a steady temperature which was lower than that of the surrounding air. The body temperature of Ligia continued to rise slowly for at least 2 hr., though remaining well below that of the environment. After 30 min. in dry air at 20 and 37° C. respectively, mean temperature depressions (of at least three readings at each temperature for each species) were, in degrees centigrade: Ligia, 2·6 and 6·8; Oniscus, 1·5 and 2·7; Porcellio, 0·4 and 1·3; Armadillidium, 0·5 and 1·8; and the cockroach Blatta, 0.7 and 2.4. The order of the Certain anomalies which appear when these figures are compared with previously established figures for insects are probably the result of differences in permeability of the integument and in the site of water loss. The ability to evaporate water rapidly, and thus to cool the body, may be of survival value when woodlice are exposed to high temperatures for short periods, particularly in littoral forms which may well have been intermediate in the evolution of terricolous from maricolous isopods.
Oviposition Behaviour in the Two Strains of the Rice Weevil, Calandra Oryzae Linn. (Coleopt., Curculionidae)
Authors: Segrove F. 
Published: April 2021

ABSTRACT
A knowledge of the biotic potential of an insect population, i.e. of its rate of multiplication under various conditions, is of obvious importance in the case of grain-infesting insects. Such knowledge is available for very few species, for its computation requires exact information of certain biotic constants (Chapman & Baird, 1934) which can be determined only by protracted experiment. Not the least important of these is one which is a function of the fertility and rate of oviposition, and the primary aim of the present investigation has been to obtain information on this subject for the rice weevil, Calandra oryzae.
Previous work on oviposition has frequently fallen short of requirement for several reasons. Where full-scale experiments have been carried out (e.g. Kunike (1936) and Lavrekhin (1937)), the control of environmental conditions has been too inadequate for the results to have any great value. Where a more rigid control has been attempted short-term experiments on rates of oviposition have usually been conducted (e.g. MacLagen & Dunn (1936), Crombie (1942), Richards and his co-workers (1944,1947)), and not infrequently selected females have been employed. The results, in consequence, though of value in other directions, are seldom if ever a reliable index of total fertility and throw little light on the general pattern of oviposition. Only in the cases of C. granaria (Eastham & McCully, 1943) and the small race of C. oryzae (Birch, 1945 a) have full data been obtained under adequately controlled conditions.
In C. oryzaeRichards (1944) has demonstrated that there are two very distinct strains which differ principally in size, and one of these, the small strain, has already been the subject of full investigation (Birch, 1945 a, b). In the present work, there-fore, attention has been mainly directed towards the behaviour of the large strain, a limited number of parallel experiments being carried out with the small weevil for comparative purposes.
The Colour Change of the Minnow (Phoxinus Laevis AG.)*
Authors: Healey E. G. 
Published: April 2021

ABSTRACT
Records were made of the times required for the melanophores of the normal minnow to reach equilibrium when the fish is transferred from one to another of the following conditions : on an illuminated white background; on an illuminated black background; in darkness. These times give further evidence of the parts played by nervous and hormonal mechanisms in the colour change of the minnow. After section of the spinal cord between the 5th and the 12th vertebrae the fish darkens but gradually becomes pale again if kept on an illuminated white background. Such fish can still show a slow colour change: dark on a black background, pale on a white background and intermediate in darkness. Observations of the times required for these colour changes in the spinal minnow show that these no longer resemble those associated with the unoperated fish; rather, they resemble the time intervals associated with amphibian colour change. Further consideration of the times required for colour change in the spinal minnow indicate that there is not only a hormone causing aggregation of the melanophores but also a hormone causing melanophore dispersion. The part played by double innervation of the melanophores is considered.
The Distribution of Electromotive Forces in the Neighbourhood of Apical Meristems
Authors: McAulay A. L. , Ford J. M. , Hope A. B. 
Published: April 2021

ABSTRACT
A research is described using different methods of experiment on two contrasted types of apical meristems with the object of measuring the permanent electrical field inside and outside the plant in the neighbourhood of the apical meristem under conditions of specified control. Most of the experiments were performed on 3-5-day-old maize seedling roots and turnip seedling hypocotyls. The conditions of measurement were such as to produce minimum stimulation of the plant. The general results were checked by experiments with other plants. The measured p.d. is a result of e.m.f.’s which are unchanged when supplying current of the order of 10−8 amp. through external conductors. Both turnip hypocotyls and sections of couch grass stems generate power of the order of 10−9 W. without polarizing (see text). In these experiments the equivalent resistance of the plant materials obeyed Ohm’s law. The average potential gradient along the surface of thirty-four turnip hypocotyls in the neighbourhood of the apical meristems was found to be 7·1 ±3·8 mV./mm. (over 6-8 mm.). The surface of the meristematic region is positive to that of older tissue. The corresponding average for twenty-five maize roots was 5·7 ± 2·4 mV./mm. (over 6—8 mm.). There are transverse e.m.f.’s between the outside and inside of the plants distributed radially from the stele to the root exodermis and hypocotyl epidermis. The inside is always negative with respect to the outside. The radial e.m.f. is larger in the meristematic region than elsewhere: In turnip hypocotyls, the radial e.m.f. at the meristematic region varies between 44 and 103 mV. ; 5−10 mm. from the apex it is 17−60 mV. In maize roots, the corresponding figures are 17−77 and 6−33 mV. There is a small but possibly not significant potential change along the axis in both the organs considered, possibly 1 mV./mm. Under the conditions of the experiment, the interior of the meristem was found to be negative with respect to the rest of the axis. Points 4 and 5 are summarized in Fig. 4A. The theory that the interior of a mass of meristematic tissue is electrically negative to older tissue is discussed in the fight of the experimental evidence and with regard to the limitations of the technique used.
Observations on the Distribution of Inorganic Phosphorus, Soluble Calcium and Soluble Magnesium in the Stomach of The Sheep
Authors: Garton G. A. 
Published: April 2021

ABSTRACT
In a preliminary survey of the distribution and fate of phosphorus-containing compounds in the alimentary tract of the sheep it was decided to estimate the inorganic phosphate levels of the fluid of the various divisions of the stomach. Information on this topic is very scanty, the only figure for phosphorus in sheep rumen liquor which could be found in the literature being 87 mg. P/100ml. (Brünnich & Winks, 1931). The initial experiments showed that inorganic phosphate occurred in higher concentration in abomasal liquor than was anticipated, and this led to an examination of the levels of soluble calcium and magnesium. Calcium and magnesium were chosen because their fate in the alimentary tract is often closely linked with that of inorganic phosphate. Some observations on the composition of sheep gastric juice were also made as one of the animals available for this investigation had an abomasal pouch of the Hollander type.
Water Uptake and Moulting in Bufo Regularis Reuss
Authors: Ewer R. F. 
Published: April 2021

ABSTRACT
In Bufo regularis Reuss moulting is accompanied by an increase in the rate of water uptake through the skin. An increase in urine flow is also observed, starting some time after the rate of water uptake has begun to increase. No increase in rate of water uptake occurs following thyroxine feeding on 4 successive days. The possibility that posterior pituitary activity is responsible for the observed increase in rate of water uptake during moulting is discussed.
The Fertilization Reaction in the Sea-Urchin
Authors: Rothschild Lord , Swann M. M. 
Published: April 2021

ABSTRACT
Unfertilized eggs of the sea-urchin (Psammechinus miliaris) were left for known but varying times in contact with homologous sperm suspensions containing known numbers of spermatozoa. Counts were made of the numbers of fertilized and unfertilized eggs at times ranging from o to 300 sec. after mixing. If spermatozoa are considered as particles moving in random directions, the frequency of sperm-egg collisions can be calculated if the density and mean speed of the sperm suspension are known. The information in (1) and (2) enables an estimate to be made of the probability of a successful sperm-egg collision. The estimated probability of a successful collision, p, varies with sperm density, d. At the lowest density used, 7·44 ×104/ml., p was found to be 0·226. At the highest density, 9·62 ×106/ml., p was about 0·011. The inverse relationship between p and d may be due to sperm-sperm interactions of a physical nature. The presence of jelly round the eggs increases p. This disposes of the possibility, raised in the past, that egg jelly may have an adverse effect on the fertilizing capacity of homologous spermatozoa under normal conditions of fertilization. The technique of subjecting eggs to a pre-determined number of collisions facilitates investigation of the conduction time of the block to polyspermy. Preliminary experiments suggest that the conduction time may be of the order of seconds rather than fractions of a second. Sources of error arising from the ‘kinetic ‘treatment of sperm suspensions are discussed in detail. One source of error concerns the alleged chemotaxis of spermatozoa towards eggs and egg secretions. No chemotaxis was observed.
Protoplasmic Structure and Mitosis
Authors: Swann M. M. 
Published: April 2021

ABSTRACT
The present paper is the first of a series dealing with the birefringence of mitotic figures in the eggs of the sea-urchin Psammechinus miliaris. Living eggs have been examined using time-lapse photography, and retardation curves for the mitotic figures constructed from densitometrie measurements made on the film negatives. In the case of the aster, an integral equation relating retardation and coefficient of birefringence can be formulated and solved exactly to give coefficient of birefringence. In the case of the spindle, coefficient of birefringence can only be calculated approximately. In both asters and spindles, the coefficient of birefringence is nil at the centres, rises to a maximum at 5 or 6 μ out, and then falls to a minimum at the equator of the spindle or the periphery of the aster. The rise in coefficient of birefringence round the centre is not as sharp as might be expected, and there is some evidence that orientation is built up gradually over a distance of a few microns. The fall in coefficient of birefringence away from the maximum is approximately an inverse square in the case of the spindle. In the aster it falls off somewhat more rapidly. Since the density of material does not vary from point to point, this fall must be due to changes in molecular and micellar arrangement, or to a decreasing proportion of oriented material. The classical conception of the spindle and asters as structures built up of discrete fibrils radiating from the centres, would be expected, for geometrical reasons, to give an inverse square fall in proportion of oriented material. While, therefore, a homogeneous structure with varying molecular and micellar arrangement cannot be ruled out, it is possible that the mitotic figure consists of definite fibrils radiating from the centres. Evidence from other sources supports this view, and suggests that the fibrils must be submicroscopic in size.
Protoplasmic Structure and Mitosis
Authors: Swann M. M. 
Published: April 2021

ABSTRACT
The mitotic figure of the sea-urchin egg is most strongly birefringent at metaphase. During anaphase this birefringence decreases considerably, but the spindle and asters both grow in size. These changes have been investigated quantitatively by constructing curves of retardation and coefficient of birefringence across the mitotic figure, using techniques described in an earlier paper. The decrease of birefringence in the spindle starts at the equator, and then moves, in the course of a few minutes, to either pole. Only when the decrease has reached the spindle poles does it begin in the asters, where it moves outwards from the centres. These changes resemble the movements of the chromosomes, which also start at the equator in metaphase, and move in separate groups to the poles during anaphase. By examining single eggs in anaphase up to the moment of fixation, and then staining them to show the chromosomes, it is established that the regions of, decreasing birefringence actually correspond to the position of the chromosomes. Since the chromosomes are too small to be the direct cause of the decrease in birefringence, it is concluded that they are producing the decrease indirectly by initiating a structural change in the spindle and asters. The possible mechanisms for this change are discussed. It is concluded that the chromosomes must be releasing an active substance, for which the term ‘structural agent’ is suggested. The growth of the mitotic figure takes the form, in the spindle, of an increase in length, and in the asters, of an increase in size. It is accompanied by an increase in coefficient of birefringence, though this is to some extent masked by the decrease in birefringence referred to earlier. The increase in coefficient of birefringence affects the whole mitotic figure from the very beginning of anaphase, and is not therefore relatable to the position of the chromosomes. For this reason it might be due to a number of different mechanisms, but as it starts at the same moment as the decrease in birefringence, it is tentatively assumed to be due to the release of a second ‘structural agent’. The increase in coefficient of birefringence is probably due to the orientation of new material. The decrease is more likely to be due to changes in molecular and micellar arrangement; it would be consistent with a contractile mechanism in the spindle. The implications of these findings are discussed in a concluding section.
Factors Determining the Temperature of Terrestrial Arthropods in Sunlight
Authors: Parry D. A. 
Published: April 2021

ABSTRACT
A study has been made of the factors determining the temperature of terrestrial arthropods in sunlight. For such animals the most important forms of heat exchange, which determine the equilibrium temperature, are radiation and convection. Compared with these, evaporation and metabolism are insignificant except under unusual circumstances. Convection depends on the size of the body in such a way that the temperature of similar animals in similar circumstances will vary as about the square root of the linear dimension. Other morphological features affecting temperature are shape, orientation and colour. The factors on which such animal temperatures depend are difficult to measure, and it is unlikely that temperatures will ever be accurately deduced from heatbalance considerations. But the insignificance of metabolism and evaporation implies that the temperature of the living animal in a given situation is likely to be very similar to that of an inanimate body of the same approximate size, shape, colour and orientation. If the temperature of such a body can be measured it forms a type of thermometer giving information of direct biological significance. Terrestrial arthropods may be as warm as, or warmer than, the ‘warm-blooded animals, particularly on the ground where conditions change rapidly over small distances so that animal temperatures must be profoundly affected by behaviour. Laboratory data on evaporation at high temperatures do not apply directly to conditions in the field, because an animal warmed by the sun will not necessarily lose water at the same rate as one warmed to the same temperature by warm air at the same relative humidity.
The Growth of Brown Trout (Salmo Trutta Linn.)
Authors: Brown Margaret E. 
Published: April 2021

ABSTRACT
Studies of scale development in fishes which live in temperate zones have suggested that variations in the rate of growth of the fish may lead to the development of annuli and circuli on the scales. These variations in growth rate might result from : seasonal variations of the physical environment, especially of temperature and illumination;variations in the quality and quantity of the food supply; andphysiological changes within the fish, such as annual cycles of maturation of the gonads and spawning. The second and third factors might well be related ultimately to the first.
Body Size in Relation to Oxygen Consumption and Pleopod Beat in Ligia Oceanica L.
Authors: Ellenby C. 
Published: April 2021

ABSTRACT
Male Ligia oceánica were used in an investigation of the relationship of body size to rate of oxygen consumption and pleopod beat. Animals varied in weight from 0·04 to 1·03 g. and from 0·95 to 3·1 cm. in length. Body shape does not change significantly over the size range, for length and breadth both increase at the same rate, and pleopod dimensions bear a constant relation to body length. Specific gravity also is constant, for the relation of body weight to the cube of body length shows no trend with increasing size. Oxygen consumption per gram decreases with increasing size and is proporitional to the –0·274 power of body weight. Total oxygen consumption is therefore proportional to the 0·726 power of body weight; but this value does not differ significantly from two-thirds. As shape is constant, surface area is proportional to the square of a linear dimension. It is shown that oxygen consumption per unit of length2 is constant over the size range. Although body length was measured far less accurately than body weight it is shown that it assesses ‘body size’ more accurately. Rate of pleopod beat was measured at 15 and 25° C. ; it decreases with the size of the animal. At 15° C. time per beat varies as the 0°66 power of body length, and at 25° C. as the 0·59 power; neither of these values differs significantly from 0·5. Despite the fact that pleopod movement is heavily damped, the rate therefore varies like that of a pendulum. Theworkof Fox (1936–9) and Fox et al. (1937a) on the rate of oxygen consumption of animals from cold and warmer seas and from different habitats is considered. It is suggested that many of their comparisons are invalidated by differences in body size of the animals concerned, and that, in relation to environment, no basis, theoretical or experimental, has been established for a distinction between ‘non-locomotory’ and ‘activity’ metabolism.