bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental Factors Influencing the Induction and Termination of Diapause in the Emperor Dragonfly, Anax Imperator Leach (Odonata: Aeshnidae)
Authors: Corbet Philip S.
Published: April 2021

Preliminary experiments have been conducted to determine the environmental factors influencing the induction and termination of diapause in the Emperor Dragonfly, Anax imperator Leach. A facultative diapause is located in the final larval instar and takes the form of an interruption of morphogenesis such that, at about 230 C., metamorphosis does not occur until some 105 days after ecdysis. In non-diapause larvae this period is about 30 days. Feeding continues during diapause development. Diapause appears to be determined in the first few days of the final instar. It can be induced by decreasing photoperiods, irrespective of the lengths of day involved, and alsoby a regime of unchanging photoperiods of a length corresponding to 31 July. Diapause can be prevented by exposure to an increase in photoperiod immediately after ecdysis. This may take the form of a single large increase (of more than 20 min.), or of successive small increments such as occur naturally in March and April. It is possible that under unnaturally long photoperiods larvae do not respond normally to regular increments. Ecdysis to the final instar appears to be stimulated by photoperiods of slightly more than equinoctial length. This tends to localize the sensitive stage to seasons when changes in day length are most pronounced. A previous exposure to winter temperatures in the penultimate instar is not necessary for diapause to be averted in spring. It is likely that diapause development proceeds most rapidly at a temperature near io° C. Negligible diapause development had occured after exposure to 6° C. for 12 weeks, although variation in the period necessary for its completion was then reduced. Diapause development has already been completed in nature by February. After this, metamorphosis occurs as a simple response to adequate temperature and food. It cannot take place when the average temperature is below n° C. Metamorphosis is not prevented by a regime of decreasing photoperiods.
The Water Relations of Earthworms
Authors: Roots Betty I.
Published: April 2021

The water content of Lumbricus terrestris, after keeping on moist filter-paper for 3 or 4 days, is 84-8 % of its body weight. That of Allolobophora chlorotica is 80 % of its body weight. Both species can survive a loss of 60 % of the body weight, but not much more. Earthworms of the species A. chlorotica, A. terrestris f. longa, Dendrobaena subrubicunda, L. rubellus and L. terrestris are all able to survive from 31 to 50 weeks in soil totally submerged beneath aerated water. The same species, and A. caliginosa can survive for 72-137 days in aerated tap water without food. Garden specimens of A. chlorotica make U-shaped burrows in soil beneath water. They do not irrigate either the burrows or glass tubes. Egg-cocoons of A. chlorotica, taken from culture pots of soil, will hatch under water and the young worms will feed and grow though totally immersed. D. subrubicunda, L. rubellus and L. terrestris avoid immersion in water when allowed a choice between water-saturated and moist but air-filled soil. When A. caligmosa, A. chlorotica and A. terrestris f. longa are allowed a similar choice, a small proportion of the population is always found in the water-filled soil. Enforced submergence before being allowed a choice of environment does not affect the behaviour of L. rubellus, i.e. water is still avoided. Similar treatment of A. chlorotica and L. terrestris results in a more frequent choice of water. It is unnecessary to postulate that the individuals of A. chlorotica occurring in Lake Windermere constitute a ‘biological race’. The avoiding reaction of earthworms to immersion may explain why they leave the soil after heavy rain.
The Quantitative Nutritional Requirements ofDrosophila Melanogaster
Authors: Sang James H.
Published: April 2021

A technique for sterilizing large numbers of Drosophila eggs is described. This gives about 95 % successful cultures. Using this method, dose-response curves have been obtained for all the main dietary constituents under conditions in which interactions between them are likely to be of little significance. Responses to the following are detailed : casein, fructose, cholesterol, lecithin, RNA, thiamine, riboflavine, nicotinic acid, pantothenic acid, biotin, pyridoxine, folic acid, choline and a water-soluble fraction of yeast which improves growth. Other substances which have been included in Drosophila media are shown to have no value for the inbred strain of flies tested. It is also shown that only K, P, Mg and Na salts need to be included in the food. On the basis of these findings an optimal medium is formulated which allows larval development to be completed in about 4 4 days. This compares with 4-1 days when the same strain is reared on an optimal supply of killed yeast. The minimal nutritional requirements of Drosophila larvae are shown to be considerably less than those of other aseptically cultured insects and, as far as the vitamins are concerned, only broadly related to the amounts found in yeast. The possible reasons for this are discussed.
The Epicuticular Wax Layers of the Pupa ofTenebrio MolitorL.
Authors: Holdgate M. W. , Seal M.
Published: April 2021

A study has been made of the structure of the outer epicuticle of the pupa of Tenebrio molitor (Coleoptera), particular attention being paid to a surface wax layer. In this study two electron optical techniques, reflexion electron microscopy and electron diffraction, have been used. At moulting, the Tenebrio pupa has a wax layer exposed on its surface. The nature of this wax has been investigated by electron diffraction. Most of the wax melts at about 40° C, and there is no indication of a ‘transition’ below this temperature. A cement layer is secreted soon after moulting. Later, a surface wax layer, made up of numerous fine filaments, appears. These filaments melt at about 80° C, and are removed by wax solvents. Material obtained from chloroform washings of mature pupae shows a wide range of melting-points, but an investigation by electron diffraction provides no evidence for a ‘transition’. The validity of the concept of a ‘critical temperature’ in the water-loss curves is discussed. The experimental data can in every case be fitted by smooth and continuous curves. It is, therefore, suggested that any physical changes (e.g. melting) which may occur in the epicuticular waxes, take place over a range of temperatures rather than at a definite ‘critical temperature’. The water-loss curves for Tenebrio pupae change shape as the outer epicuticle develops. Mature pupae show good waterproofing to a higher temperature than do young pupae. This change in the curves is associated with the secretion of the cement layer. Parallel studies have been carried out on Rhodnius nymphs and similar results obtained.
Studies On the Respiration of Sea-Urchin Spermatozoa
Authors: Mohri Hideo
Published: April 2021

In the previous paper (Mohri, 1956), it was shown that in sea-urchin spermatozoa, the outburst of respiration which occurs on dilution of a sperm suspension can be suppressed by sodium azide. However, the low respiration which follows the outburst is not affected by this poison, although both are inhibited by cyanide.
The Nerves and Muscles of Medusae
Authors: Horridge G. A.
Published: April 2021

The compensatory movements of Cyanea (Semaeostomeae) and Cassiopea (Rhizostomeae) are described. The asymmetry of these responses is not compatible with the properties of the through-conducting giant fibre net which propagates the contraction wave. Stimulation experiments with Cyanea show that a second nerve net, called the diffuse net, acts locally on the muscles of the bell and delays the process of relaxation. In Cassiopea, the responses of a ring of tissue containing a continuously circulating contraction wave are also evidence of a double innervation. The responses of Nausithose (Coronatae) are described and are interpreted in a similar manner. In all three orders the two nerve nets are in places superimposed but are independent except where they meet at the marginal ganglia. Here the diffusenet acts irreversibly on the rhythmical units, which are known to be within the giant fibre net.
Nitrogenous Excretion by Embryos of the Viviparous Snake Thamnophis S. Sirtalis (L.)
Authors: Clark Hugh , Sisken Betty Florio
Published: April 2021

Functional considerations of the placenta of saurian reptiles are limited virtually to assumptions based on known embryonic requirements and structural placental features (Weekes, 1935). It appeared that the nature of embryonic excretion might profitably be investigated in the garter snake whose young are born alive. The extreme solubility of urea, and the fact that the black snake embryo excretes only 20% of its nitrogenous waste as uric acid (Clark, 1953), suggest the possibility that embryos of a placental saurian reptile might pass urea and ammonium salts to the blood stream of the mother; whether some of the soluble nitrogenous excreta are eliminated through the placenta or whether all nitrogenous excreta are retained in the foetus and adnexa, the degree to which the embryo is dependent upon uric acid is of interest. Accordingly, assays of urea, ammonia and uric acid in the developing embryo were undertaken.
Some Aspects of the Growth of Single and Mixed Populations of Flagellates and Ciliates
Authors: Mučibabić Smilja
Published: April 2021

The effect of temperature has been studied more than that of any other single ecological factor, and its significance for the growth of populations of many species has been known for a considerable period. Previous studies on Protozoa have been confined to the effect of temperature on the rate of division, and so far as is known other aspects of the problem have not as yet been examined. Thus,Woodruff & Baitsell (1911) and Mitchell (1929) examined the effect of temperature on the division rate of Paramecium in cultures containing bacteria. This effect was also studied on Chilomonas paramecium in isolation cultures by Smith (1940),and on Tetrahymena geleii by Phelps (1946). Phelps observed division rates only in the logarithmic phase of growth, and in that work he was not concerned with the effect of temperature on population growth. It seemed worthwhile, therefore, to examine the effect of temperature on the growth of Chilomonas paramecium in greater detail.
Proprioception in Limulus
Authors: Pringle J. W. S.
Published: April 2021

Tonic and phasic discharges of impulses may be recorded in the small leg nerve of Limulus from endings sensitive to the position and movement of the femorotibial and other joints. The nerve fibres originate from the large sensory cells described by Stuart (1953)-Of those at the femoro-tibial joint, one group of cells lies under the hinge and the endings react tonically to the strains present in the cuticle ; some are excited by flexion and some by extension. The other group of cells, lying more internally, have endings in the connective tissue and react phasically only during joint movement. The relationship is discussed between these endings and the lyriform organs of Arachnids and the campaniform sensilla of insects.
Excretion by the Malpighian Tubules of the Stick Insect, Dixippus Morosus (Orthoptera, Phasmidae): Calcium, Magnesium, Chloride, Phosphate and Hydrogen Ions
Authors: Ramsay J. A.
Published: April 2021

The excretion of calcium, magnesium, chloride, phosphate and hydrogen ions has been studied in preparations of single Malpighian tubules isolated in drops of serum under liquid paraffin. The concentrations of calcium, magnesium and chloride are always lower in the urine than in the serum. The concentration of phosphate is always greater in the urine than in the serum. As the concentration of phosphate in the serum increases, the rate of urine flow also increases. The urine is always alkaline to the serum but becomes acid in the rectum. The general problem of excretion by Malpighian tubules is briefly reviewed and discussed.
Visual Responses by Octopus to Crabs and Other Figures Before and After Training
Authors: Young J. Z.
Published: April 2021

Octopuses were fed for some days with fishes in their homes at one end of the tank, and the effect of figures shown at the opposite end was tested. Any small moving object may then be attacked, but the probability of attack is low and the delay long. Crabs and a black horizontal rectangle were attacked more often than other figures. If a figure is withdrawn on the occasions when it is attacked, then the probability of attacks remains low and may slowly decrease. If the octopus is allowed to eat crabs the probability of attacks on them quickly rises towards unity. If food is given when some other figure (say a black vertical rectangle) is attacked, then this figure will later be attacked. An octopus makes attacks more regularly on a figure that has recently been associated with food than on any other figure. This learning to attack a given figure can take place after removal of most of the vertical lobe, but the learning is slower and responses less accurate than in the normal animal. Octopuses from which the vertical lobe has been removed attack crabs more readily than other figures. The system that ensures attack therefore resides elsewhere, probably in the optic lobes. If shocks are given when a previously neutral figure is attacked, then the probability of further attacks on this figure rapidly approaches zero. Attacks on other figures or crabs remain frequent. If the vertical lobe is then removed, no attacks are made on such an originally neutral figure. If a figure that has been associated with food is then rewarded with shocks, the probability of attack falls more slowly than if the figure had been neutral. If the vertical lobe is now removed, the frequency of attacks rises. The memory preventing attack is therefore partly resident in the vertical lobe. The greater the amount of previous training to attack, the more slowly does the animal learn not to attack. This applies also if the training to attack is given after vertical lobe removal. After vertical lobe removal, shocks given when crabs are attacked rapidly reduce the probability of attack if the octopus had not previously eaten crabs while in the laboratory. If such feeding had taken place, the probability of attack falls only slowly without the vertical lobes. The experiments show that information stores associating a given figure with either food or shock can be set up after removal of the vertical lobes but tend to dissipate more rapidly than in a normal octopus.
The Effects of Salinity Changes on the Respiratory Rate of the Prawn Palaemonetes Varians (Leach)
Authors: Lofts B.
Published: April 2021

Palaemonetes varians, variety microgenitor, commonly inhabits only saline water around the British coast. It is, however, abundant in water of extremely low salinity in the Cardiff area, where it occurs in the drainage ditches of farm land adjacent to an area of salt-marsh. Animals from areas of both high and low salinity were subjected, in the laboratory, to a range of salinities varying from pure tap water to concentrated sea water. The rate of respiration at each salinity was measured. The population that inhabited the almost fresh water in the ditches differed physiologically from the salt-water form, although morphologically they were identical. The salt-water population showed a minimum respiratory rate when in a medium of 26‰, NaCI salinity. This was expected, since the animal is isotonic at this salinity and the osmoregulatory work is minimal. The second population respired least when in a medium of 6‰o NaCI. The significance of this is discussed.
Investigations Into the Distribution of Blood in the Heart and Aortic Arches of Xenopus Laevis (Daud.)
Authors: De Graaf A. R.
Published: April 2021

The structure of the heart of Xenopus laevis is described, and the differences between Xenopus and Rana are stressed. A fluorescein-cinematographic method of tracing blood flow and an optical manometer for the measurement of blood pressure in Xenopus are described. The right atrial blood is absorbed into the trabecular meshwork only on the right side of the ventricle. Whereas the output of the right atrium is not, or only in negligible quantities, transferred to the left side of the ventricle, a considerable proportion of the output of the left atrium moves to the right half of the ventricle. The left atrium has a larger output than the right atrium. Almost all the blood expelled from the right atrium is sent to the pulmo-cutaneous arches. The blood from the left atrium is distributed to all the arterial arches and the pulmo-cutaneous arches receive a considerable proportion of this blood. More blood flows through the pulmo-cutaneous arches at each beat than is sent through the carotid and systemic arches together. The rate of flow in the pulmonary circuit is much higher than that in the body circuit. A physiological connexion is demonstrated between the left side of the ventricle and the systemic and carotid arches, and between the right side of the ventricle and the pulmo-cutaneous arches. Pressures in the pulmo-cutaneous arch are consistently lower than in either the carotid or systemic arches. The pressures in the carotid and systemic arches are remarkably similar. There is, therefore, no sound reason for postulating a mechanism in the carotid labyrinths which should maintain a higher pressure in the carotids than in the systemics. The pulse curves in the arches show two waves: the first, major, one produced by contraction of the ventricle, the second one by contraction of the bulbus cordis. The spiral valve may not come into contact with the opposite wall of the bulbus before contraction of the latter. Before that time, i.e. as long as the major propulsive force of the ventricular contraction is not expended, the cavum pulmo-cutaneum is in open communication with the ventricle. The pulmonary veins show a weak pulse, and their pressure is higher than in the hepatic veins. This indicates smaller resistance in the pulmonary circuit than in the body circuit. The selective distribution is neither in agreement with the ‘classical theory’ nor with ideas of random distribution. The forces underlying the selective distribution and the significance of the pattern are discussed.
Periodism and Energy Summation with Special Reference to Flight Rhythms in Aphids
Authors: Johnson C. G. , Taylor L. R.
Published: April 2021

Summer populations of Aphis fabae often show a bimodal flight curve with no flight at night. The teneral period between moulting and flight depends on temperature and can be estimated. Increase in temperature causes the teneral period to shorten and is followed, some time later, by an increase in rate of take-off. This produces the afternoon peak of flight. The morning peak is usually due to aphids which, maturing overnight, accumulate and fly when rising temperature permits. A graphical method is given for constructing flight curves from constant, or observed, moulting rates and the temperature during the teneral period. Population periodicities in which each individual acts only once, are distinguished from individual periodicities in which the same act is repeated by the same individuals. Synchronization is necessary for either type to be evident, and this may be due to rhythmic fluctuations in developmental increments preceding the act, even in short-term periodicities, rather than to behaviour responses. This may apply to rhythms of flight, as in aphids, or of emergence ; to seasonal periodic growth of populations in insects; or to populations of cells in regulatory organs.
Osmotic Conditions During the Embryonic and Early Larval Life of the Brook Lamprey (Lampetra Planeri)
Authors: Hardisty M. W.
Published: April 2021

Observations have been made on the swelling of eggs in tap and distilled water. The rate of uptake of water through the outer membranes and the surface of the ovum fell off sharply within a short time of contact with water. In distilled water uptake into the perivitelline space was very much greater than in tap water, but there were no significant differences in the volume of the ovum itself in these two media. The initial permeability of the ovum to water has been estimated as 0.049 μ3/μ2atm./min., falling after about 7 hr. to 0.003 and remaining at this level for the first 5 days of development. The outer egg membranes are apparently freely permeable to water and ions, and the mean Cl concentration of the perivitelline fluid in the later stages of development was found to be only 2.4 mM/l. Evidence is presented which points to a decrease in the volume of the embryo at some point between gastrulation and hatching. In tap water a contraction of the whole egg was observed from the fifth day onwards. The water content of the embryo at hatching was not very much greater than that of the ovarian egg. After hatching, until the absorption of the yolk, there was a continuous increase in the fresh weight and water content of the ammocoetes. The evidence suggests that the ovarian egg is in osmotic equilibrium with the peritoneal fluid (mean 110 mM/NaCl/l.). During development the osmolar concentration of the total egg fluid was reduced to values similar to those calculated from the known dilution, i.e. 30-40 mM/l. At hatching, the osmolar concentration of the embryo (80 mM/l.) was raised within a few days to 11-120 mM/l. The observed reduction in Cl concentration of the whole egg was much greater than that calculated from the increases in volume. The Cl concentration of the embryo itself was reduced from an initial value of 56 to 15 mM/l. embryo fluid a week before hatching. Determinations of the total Cl content of whole eggs and embryos showed a very marked loss of Cl ions in the two days following fertilization. Within 35 days after hatching the Cl level had been raised by active uptake to about four times the values at the time of hatching."
The Chloride Regulation of the Brackish and Fresh-Water Races of Mesidotea Entomon (L.)
Authors: Lockwood A. P. M. , Croghan P. C.
Published: April 2021

Mesidotea entomon (L.) is found in the Baltic and in certain fresh-water lakes in Sweden. It is believed that colonization of fresh water in this region has taken place since the last Ice-age. In the present work animals from brackish and fresh-water habitats have been compared both in respect of the concentration of chloride in their haemolymph and of their ability to survive in media of various salinities. Both fresh-water and Baltic animals have been found able to survive in Plymouth sea water, the concentration of chloride in their haemolymph being close to the concentration of chloride in this medium. Baltic animals could not be acclimatized to fresh water. Animals from both habitats have the same general level of chloride concentration in their haemolymph when acclimatized to dilute sea water. These results are discussed in relation to the evolution of a fresh-water race from a brackish-water race.
Observations On the Normal Histology and Histochemistry of the Fat Body of the Locust (Schistocerca Gregaria)
Authors: Coupland R. E.
Published: April 2021

The fat body of the locust Schistocerca gregaria is composed of both fat cells and oenocytes. The cells increase in number by mitotic division. Glycogen, proteins and phospholipids are present in all cells but are most abundant in the oenocytes ; the amounts of these substances are less in the adult than in the immature forms, whereas uric acid is more abundant in the adult.

Small mitochondria-like structures (as judged by their staining reactions to Janus Green B and acid-fuchsin-methyl green) have been observed in the cytoplasm of the fat cells, the oenocytes, the Malpighian tubules and the follicular cells of the ovary.

No micro-organisms have been observed.
Components of Nitrogenous Excreta in the Earthworms Lumbricus Terrestris, L. And Eisenia Foetida (Savigny)
Authors: Needham A. E.
Published: April 2021

This work was undertaken initially in order to obtain normal standards of comparison for the pattern of nitrogen excretion during wound healing and regeneration in earthworms. The main interest in the results, for the present purpose, lies in the contrast between the patterns of nitrogen output in the two species. The pattern of excretion in Lumbricus is quite well known, from the studies of Lesser (1908), Delaunay (1934) and his colleagues, and Cohen & Lewis (1949a, b, 1950); there is also some information about Pheretima (Bahl, 1945, 1947) and about some representatives of other classes of the Annelida (see Prosser et al. 1950), but none of these results have anticipated the great contrasts here observed between two rather closely related genera. A certain amount of work has been done also on Allolo-bophora caliginosa (Savigny), but this will not be described in detail.
A Temperature Receptor in the Tarsus of the Cockroach, Periplaneta Americana
Authors: Kerkut G. A. , Taylor B. J. R.
Published: April 2021

This paper describes the electrical responses of the isolated limb of the cockroach following localized warming and cooling. There is a temperature-sensitive region in the pad between the claws, and in the first, second, third and fourth tarsal segments (the arolium and the pulvilli). The preparation becomes more active when the temperature is lowered below 13° C. The activity increases as the temperature drop increases. It thus behaves like a cold receptor. The preparation is sensitive to a drop in temperature of i° C. over the critical range below 13° C. The preparation is stimulated by warming it approximately 5° C. in the range 0-28° C., but the activity lasts for only a short time. Warming the preparation above 30° C. brings about considerable prolonged electrical activity.
Effects of High Hydrostatic Pressures on the Activity of Flagellates and Ciliates
Authors: Kitching J. A.
Published: April 2021

The effects of brief exposure to high hydrostatic pressures, ranging in some cases up to 18,000 p.s.i. (1225 atm.) has been studied in various flagellates and ciliates. Closely related species may react very differently. In general high pressure depresses flagellar or ciliary movement, and in most cases, under the standard conditions of the experiments, all movement soon stopped at 8000-14,000 p.s.i. (544-953 atm.). The pressure required to stop movement was usually near that which caused visible structural damage (Table 1, p. 508). Movement was restored on release of pressure provided that the treatment had not been too drastic. In the case of one peritrich ciliate (Epistilis plicatilis) a moderate pressure (1000-3000 p.s.i., or 68-204 atm.) caused an increase of ciliary frequency, but at still higher pressures the frequency was drastically reduced. There is evidence that behaviour was affected by moderate pressures, quite apart from changes in the intrinsic activity of flagella or cilia. Certain flagellates and ciliates were stimulated to activity by application of moderate pressures, and others became motionless. Spirostomum ambiguum was deprived of its ability to reverse or make the avoiding reaction while at high pressure, and at certain pressures the cirri of the hypotrich Stylonychia mytilus beat in a wild and uncontrolled way. It is suggested that high pressure affects ciliary co-ordinating mechanisms in various Protozoa.
The Growth and Development of Mice in Three Climatic Environments
Authors: Biggers J. D. , Ashoub M. R. , McClaren Anne , Michie Donald
Published: April 2021

Pregnant mice were placed in rooms at three different environmental temperatures: hot, temperate and cold. The hot and cold environments were less favourable than the temperate as judged by incidence of both prenatal and postnatal mortality of the young. The growth and development of the young was studied during the first 4 weeks of life.

Body weight was expressed on the logarithmic scale throughout, and since males were found to be significantly heavier than females the two sexes were considered separately. The inverse relation between body weight and number of mice in a litter, reflecting competition between litter mates, was particularly marked in the cold and was still increasing 4 weeks after birth. In the hot and temperate environments the effect reached a maximum at 2-3 weeks of age.

When allowance had been made for the effect of litter size on body weight, no significant differences in rate of growth or development were found between the mice in the hot and temperate environments. Both growth and development were markedly retarded in the cold."
Chemotaxis of Bracken Spermatozoids
Authors: Brokaw C. J.
Published: April 2021

In the original experiments on the chemotaxis of fern spermatozoids, Pfeffer (1884) inserted small glass capillaries filled with a sodium malate solution into suspensions of spermatozoids, and observed that chemotactic aggregation resulted from precise orientation of the spermatozoids to the gradients produced by diffusion of malate from the open tip of the capillary. More recently, Rothschild (1952) provided definite confirmation of the precision of orientation in a chemical gradient by cinemicrographic records of chemotaxis, using bracken spermatozoids.
The Mechanism of Osmotic Regulation in Artemia Salina (L.): The Physiology of the Branchiae
Authors: Croghan P. C.
Published: April 2021

The uptake of silver ions by Artemia has been investigated. The staining is localized to the first ten pairs of branchiae. There is no staining of the eleventh pair or of any other part of the animal. The uptake of silver is due to a purely passive precipitation of AgCl within the thickness of the branchial cuticle. The effects of KMnO4 and methylene-blue solutions have also been studied. Their effect is localized to the epithelium under the cuticle of the first ten pairs of branchiae. It is concluded that all these staining reactions demonstrate that the cuticle over the first ten pairs of branchiae is the only part of the external cuticle that is appreciably permeable. Animals whose branchial epithelium has been damaged by a brief exposure to saturated KMnO4 solution have lost the ability to osmo-regulate. They are closely isotonic with their medium, and the range of external concentration tolerated is much restricted. This isotonicity is not due simply to increased permeability, but is due to specific destruction of the mechanism normally excreting NaCl in hypertonic media. Correlation of the physiological effects of KMnO4 treatment with the sharp localization of damage, and the evidence for localized permeability indicates that the epithelium of the first ten pairs of branchiae is the site of active NaCl excretion in hypertonic media, and probably of active uptake from hypotonic media. The ontogeny of this mechanism is traced. In nauplii the dorsal organ is apparently concerned in NaCl excretion. When the branchiae develop the dorsal organ degenerates.
The Mechanism of Osmotic Regulation in Artemia Salina (L.): The Physiology of the Gut
Authors: Croghan P. C.
Published: April 2021

Artemia is continuously swallowing its medium, whether it is hyper-, iso-, or hypotonic to the haemolymph, and taking up water from the gut lumen. The osmotic pressure of the gut fluids is appreciably greater than that of the haemolymph, but in the more concentrated media is considerably below that of the medium. This indicates that considerable amounts of NaCl must be passing across the gut epithelium into the haemolymph. The concentration of both sodium and chloride ions in the gut fluids is always less than that in the haemolymph, indicating that there must be an active uptake of NaCl across the gut epithelium. 4. It is considered that the gut of Artemia has become adapted as a mechanism for the active uptake of water, controlling water balance and preventing dehydration in hypertonic media. 5. The adaptations for maintaining the NaCl and the water balances in Artemia are compared to those found in the marine teleosts, and are shown to be extremely similar.
Studies On the Feeding and Nutrition ofTuberolachnus Salignus(Gmelin) (Homoptera, Aphididae)
Authors: Mittler T. E.
Published: April 2021

Several workers have tried to ascertain the nitrogenous and carbohydrate materials which are ingested by aphids and coccids by analysing juices, phloem exudates and extracts obtained from the insects’ host plants (Evans, 1938; Michel, 1942; Lindemann, 1948; Auclair & Maltais, 1950, 1952; Gray, 1952; Hackman & Trikojus, 1952; Gray & Fraenkel, 1954; Bacon & Dickinson, 1957). It remains to be established, however, whether the insects ingest materials in the same form and at the same concentration as they occur in their host plants. The present paper gives details of a method, outlined by Kennedy & Mittler (1953), for obtaining the sap which normally enters the alimentary canal of feeding Tuberolachnus salignus (Gmelin). By determining the nitrogen and sugar composition of this sap and that of the honeydew excreted by the aphid, it was possible to examine the chemical relationship existing between the insect’s food and its excreta.
The Effect of Weak Electrolyte Solutions on the Hatching Rate of the Eggs of Trichostrongylus Retortaeformis (Zeder) and Its Interpretation in Terms of A Proposed Hatching Mechanism of Strongyloid Eggs
Authors: Wilson P. A. G.
Published: April 2021

The influence of solutions of NaCl on the hatching of eggs of Trichostrongylus retortaeformis is studied. It is shown that the effects are not the consequence of colligative properties, but are related to ionic phenomena. 0·05 N-NaCl slows down the rate of hatch without impairing the ultimate ‘hatchability’of the eggs. Processes of development up to hatching are not slowed down. The effect demonstrated in the case of NaCl is shown to be shared by eight other electrolytes, the depression in the rate of hatch being proportional to the mobility of the ions in solution. On the assumption that the effect of the ions is due to a penetration of the egg membrane(s) the rate of entry is shown to be controlled by the speed of the slower ion in any one salt. The influence of NaCl on the permeability of hatching eggs to water is studied. It is shown that the rate of increase in permeability is slowed down sufficiently in NaCl to control the rate of hatch. The inference that water permeability is a necessary prerequisite for hatching is made, a further hypothetical process being invoked to account for the rate of hatch in the absence of NaCl, since it is not then controlled by changes in water permeability. The probability that the net effect of ionic solutions on the eggs is one concerned with the rate of breakdown of the inner wax-like layer of the egg is strengthened by experiments demonstrating that the depressing influence of NaCl is antagonized by ‘Teepol’, though the comparable influence of other, non-emulsifying, compounds cannot be explained. The role of water permeability in the hatching mechanism is investigated. A hatching mechanism of strongyloid eggs is proposed which involves two processes, the first dependent upon the osmotic relationships of the unhatched larva to its environment, the second being some sort of chemical weakening of the outer shell. It is suggested that the effect of ions on hatching rate assists the ‘embryonated egg’ to survive under natural conditions when the hatched first-stage larva might otherwise be destroyed by desiccation.
Tidal and Diurnal Rhythms of Locomotory Activity in Carcinus Maenas (L.)
Authors: Naylor E.
Published: April 2021

Spontaneous locomotory activity was recorded continuously for several days in Carcinus maenas (L.). A complex rhythm was observed which could be analysed into two components, one of diurnal frequency (24 hr.), with peaks of activity during the hours of darkness, and one of tidal frequency (ca. 12·4 hr.), with peaks at the time of high tide. The rhythms persist in constant dim light at constant temperatures, whether the crabs are kept moist in air or continuously immersed in sea water. The resultant effect of the two rhythms is to produce particularly high activity peaks during periods which recur with a semi-lunar frequency. Experimental results relate to observed behaviour on the shore.
The Absorption and Metabolism of Some Sugars in the Locust, Schistocerca Gregaria (Forsk.)
Authors: Treherne J. E.
Published: April 2021

The uptake of 14C-labelled glucose, mannose and fructose from the alimentary canal of Schistocerca gregaria (Forsk.) has been studied using the dye Amaranth as a reference substance. Absorption was confined to the mid-gut, the proportion absorbed by the caeca depending on the type of sugar and its concentration in the gut lumen. The absorbed sugars were converted, in varying degrees, to trehalose which accumulated in the haemolymph. The extent of the conversion appeared to parallel the rate of absorption of the sugars at the various concentrations. The sugars passed through the gut wall at similar rates in experiments in which the isolated alimentary canal was suspended in a large volume of circulating poisoned saline. The passage through the gut wall under these conditions was equivalent to the rapid absorption obtained in vivo when there was a rapid conversion to trehalose. It is suggested that these observations support the hypothesis that the sugars are absorbed by diffusion across the gut wall and that the process is facilitated by the rapid conversion to trehalose in the haemolymph, which tends to maintain a steep concentration gradient. At very low concentrations in the gut lumen, glucose was at a similar level to the relatively small amount of glucose in equilibrium with the trehalose in the haemolymph. When the specific activity of injected 14C in the haemolymph approximated to that in the gut lumen the absorption of the labelled glucose from the mid-gut caeca was reduced at very low concentrations. Thus at these levels it is suggested that most of the absorption of labelled glucose can be attributed to an exchange with that in the haemolymph. At a concentration of 0·01 M/1. the proportion exchanging became negligibly small and the absorption of the labelled glucose molecules approximated to the net glucose absorption.
Gas Secretion in Fishes Lacking Rete Mirabile
Authors: Sundnes G. , Enns T. , Scholander P. F.
Published: April 2021

In most fishes with a closed swimbladder the gas secretion is confined to a special organ, the so-called red gland, which consists of a secretory epithelium supported by a counter-current capillary system, the rete mirabile. All the fishes investigated which possess this structure are capable of accumulating oxygen, and most of them also nitrogen, in the swimbladder against a pressure gradient. In other fishes the rete mirabile is lacking, and instead the secreting epithelium lines the swimbladder directly. Many fishes in this category apparently secrete only nitrogen.
Induced Ovarian Development in Decapitated Mosquitoes by Transfusion of Haemolymph
Authors: Gillett J. D.
Published: April 2021

Ovarian development in mosquitoes appears to be under hormonal control. Evidence for this view has been derived from experiments involving removal of the endocrine organs assumed to be responsible for production of the hormone by decapitation or ligation of the thorax, before and after a critical period. (Detinova, 1945; Clements, 1956; Gillett, 1956b, 1957). Such evidence, however, even when supported by histological studies, is indirect and does not entirely exclude the possibility of alternative explanations; nor are the grounds for criticism removed when insects are joined in parabiosis (Wigglesworth, 1936, 1954; Williams, 1946). The present paper describes induction of ovarian development in mosquitoes, decapitated before the critical period, by transfusion of haemolymph from normal donors.
Effects of the ant,Lasius NigerL., on the Feeding and Excretion of the Bean Aphid,Aphis FabaeScop
Authors: Banks C. J. , Nixon H. L.
Published: April 2021

Banks (1958) confirmed that colonies of Aphis fabae, attended by the ant Lasius niger, multiply more than ant-free colonies on bean plants, in the absence of the aphids’ insect enemies. He showed that, when the aphids were ant-attended, they changed their excretion behaviour and that the normal dispersal of adult apterae from young apical growth of bean plants was delayed. No significant differences were found between the reproduction rates of individual ant-attended and ant-free aphids living on leaves of the same age, but the reproduction rates were significantly affected by the age of the plant tissue on which the aphids fed. The increased multiplication of ant-attended colonies was attributed to the delay in dispersal of adult apterae from the young growth, where they reproduced more, to the old growth, where they reproduced less.
Factors Controlling the Change of Shape of Certain Nemertean and Turbellarian Worms
Authors: Clark R. B. , Cowey J. B.
Published: April 2021

Nemerteans and turbellarians have an inextensible fibre system around them in the form of a lattice of left-and right-handed spirals. The effect of this system on the change of shape on these worms has been analysed theoretically and compared with the observed behaviour of nine species of turbellarian and nemertean from widely differing habitats. The following theoretical relationships have been studied: (a) Variation of the angle between the geodesics and the longitudinal axis of the worm during changes in length, and the role of the fibre system in limiting changes in length of the animal. (b) The change in cross-sectional shape during changes in length. (c) The extension of the fibres and the extensibility of the worms, assuming the fibres of the lattice to be elastic. The species investigated conform with the theoretical predictions to varying degrees and have been grouped accordingly : (a) Geonemertes dendyi and Rhynchodemus biUneatus have low extensibilities and fit the prediction well. They are nearly circular in cross-section at all lengths as a result of their low extensibility and this is related to their terrestrial habit and need for water conservation. (b) Amphiporus lactifloreus, Lineus gesserensis and L. longissimus are moderately flattened in the relaxed position and have extensibilities between 6 and 10. They are marine crawling forms using cilia for locomotion and so must present a fairly large ciliated surface to the substratum. The fibre system does not limit contraction; the compression of the epithelial cells causes the observed extensibilities to fall a little short of the theoretical values. (c) Cerebratulus lacteus, Malacobdella grossa, Polycelis nigra and Dendrocoelum lacteum are very flattened forms and have very high theoretical extensibilities, but very low observed ones. The factors causing this are the thickness of the body-wall musculature (Cerebratulus), the limiting effect of longitudinal and circular reticulin fibres in the muscle layers, and the presence of dorso-ventral and diagonal muscles. Their flattened form is correlated with ecological factors (with swimming in Cerebratulus, with its parasitic life in the mantle of bivalves in Melacobdella) or with physical ones in turbellarians where a permanently flattened form is necessary for these worms to move by ciliary action.
Some Experiments on Form Perception in the Nymphs of the Desert Locust, Schistocerca Gregaria Forskål
Authors: Wallace G. K.
Published: April 2021

Nymphs of the desert locust are spontaneously attracted to simple forms in the visual environment, and show a preference for certain figures. Experiments are described which analyse certain of the important properties which make a figure attractive to this insect. The insects show a preference for long straight vertical edges as opposed to short straight vertical edges. Straight vertical edges are preferred to straight oblique edges and vertical figures with straight edges are preferred to vertical figures with wavy or serrated edges. In the absence of straight vertical edges a preference is shown for the figure with the more complex contour (for figures of comparable size). It is postulated that in this insect form discrimination is based on the number of stimulus changes per unit time produced by moving contours and on the spatial and temporal distribution of such changes. The results are compared with those of previous workers and in particular with those of Hertz and of Wolf and Zerrahn-Wolf on the bee.
The Digestion and absorption of Tripalmitin in the Cockroach, Periplaneta Americana L
Authors: Treherne J. E.
Published: April 2021

A partial hydrolysis of 14C-labelled tripalmitin has been demonstrated in the crop of Periplaneta americana L. No significant absorption of tripalmitin and its derivatives could be demonstrated in the crop, whether the tripalmitin was suspended in an experimental fluid or dissolved in emulsified oleic acid. Absorption took place in the mid-gut and appeared to be largely confined to the caeca and the anterior part of the ventriculus. The total absorption of tripalmitin showed a linear relation with crop emptying, suggesting that the rate at which the material was allowed to leave the crop, rather than the uptake in the mid-gut, was the limiting factor in absorption.
Osmoregulation in the Muscle Fibres of Carcinus Maenas
Authors: Shaw J.
Published: April 2021

Measurements have been made of the freezing-point depression of single muscle fibres of Carcinus maenas and of the concentrations of the non-protein nitrogenous components of the muscle. When the blood is diluted the osmotic activity of the muscle fibres always falls in proportion. The fibres are probably always in osmotic equilibrium with the blood. The osmotic activity of the fibres can be accounted for in terms of the concentrations of the muscle ions together with nitrogen-containing compounds, such as free amino acids, taurine and trimethylamine oxide. These organic substances account for over 60 % of the total osmotic pressure. In crabs from dilute sea water the concentrations of the nitrogenous compounds are reduced below the level expected from the increase in water content of the muscle. It is suggested that the muscle fibre can prevent excessive water intake by the removal of nitrogenous substances, thus reducing the internal osmotic activity. The process is reversible. The importance of the mechanism in relation to the adaptability of the cell to reduced blood concentration is discussed.
Observations on the Temperature Regulation and Food Consumption of Honeybees (Apis Mellifera)
Authors: Free J. B. , Spencer-Booth Yvette
Published: April 2021

Bees have been kept in groups whose numbers ranged from 10 to 200 bees, at temperatures ranging from 0–40° C. At 40° C. bees in groups of 200 had a higher death-rate than bees in smaller groups. At temperatures of 25–350 C. the death-rate was low and about the same in all groups. Below 25° C. the more bees in a group, the longer they survived. The temperatures of all groups increased with that of their environment, the larger a group, the higher its temperature. The difference between the external temperature and that of the groups decreased with increase in the former until at 35 and 40° C. groups of all sizes were at or slightly below environmental temperature. At temperatures from 20–40° C. the percentage of bees in a group that were clustering was directly related to the size of their group, bees in groups of 10 or 25 hardly clustering at all. At each temperature at 15° C. or below, about the same high percentage of bees clustered in all groups. The amount of food (sugar syrup) consumed per bee increased with decrease in the environmental temperature. Very little water was drunk at environmental temperatures of 25° C. or lower but, at 35° C. and above, relatively enormous quantities were taken. These results have been discussed especially in relation to information on the temperature regulation and food consumption of colonies in winter.