bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Transpiration of Terrestrial Isopods
Authors: Bursell E. 
Published: April 2021

ABSTRACT
The transpiration of three species of Isopoda has been investigated ; Armadillidium shows the highest resistance to desiccation, Oniscus the least, and Porcellio is intermediate. The permeability of isopod cuticle is limited by lipoids which impregnate the endocuticle. If the temperature is raised above the lipoid melting-point a marked increase in permeability results. Isopods show a characteristic decline in transpiration rate during exposure to desiccating atmospheres. The high initial rate of evaporation is due mainly to loss of water from layers of the cuticle external to the lipoid barrier. There is a progressive decrease in the permeability of the integument during desiccation. This is brought about by a shrinkage of the cuticle, which leads to a closer packing of lipoid molecules. The mechanism of this structural alteration is based on an interaction between endocuticular proteins and the ionic constituents of body fluids; in the course of desiccation the blood concentration increases and there is a corresponding decrease in the dispersion of endocuticular elements.
The Function of the Lyriform Organs of Arachnids
Authors: Pringle J. W. S. 
Published: April 2021

ABSTRACT
Experiments involving the recording of impulses in sensory nerves in the appendages of a scorpion and an amblypygid show that the slit sensilla (lyriform organs) of these arachnids are mechanoreceptors, sensitive to strains in the cuticle and analogous to the campaniform sensilla of insects.
The Permeability and Structure of the Cuticle of the Aquatic Larva of Sialis Lutaria
Authors: Shaw J. 
Published: April 2021

ABSTRACT
The permeability to water of the cuticle of Sialis larvae has been measured, using heavy water as tracer. The penetration was slow, the permeability constant being only 1·8 × 10−2 cm./hr. at 20°C. There was no obvious difference between the rate of water influx and outflux. The rate at which water penetrated into the tissues from the blood was much greater than through the cuticle. The Q10 for diffusion through the body surface was high, lying between 3·0 and 3·8. The osmotic uptake of water was calculated to be about 1 % of the body weight per day at 10°C. Drinking of water did not occur in normal larvae, but in larvae with the blood volume reduced, osmotic uptake of water through the gut did take place and the gut wall was much more permeable to water than the cuticle. A similar intake of water probably occurred during moulting. The permeability of the cuticle to chloride was measured and also found to be of a low order (P= 1·04 × 10−4 cm./hr. at 17°C.). Sodium diffused out of the larva at the same rate as the chloride. Histological examination of the cuticle showed that in the abdomen it was thin and consisted of a 7 µ. thick endocuticle and a 1 µ epicuticle. Over the thorax it was thicker, and a polyphenol layer was present as the outer layer of the epicuticle. There was indirect evidence of the presence of a wax layer. Wax was extracted from the cuticle, and the thickness of the layer from which it was derived was estimated by means of a monolayer technique. In the cuticle of the abdomen and gills the thickness averaged 0·1 µ. The permeability to water of the cuticle was compared with that of terrestrial insects and was found to be much greater. This difference was not due to the thick ness of the wax layer but probably to some physical properties of the wax. The cuticle of Sialis larvae showed no ‘critical temperature’ or sudden change in the permeability properties with temperature over the range of temperatures studied.
Ionic Regulation in the Muscle Fibres of Carcinus Maenas
Authors: Shaw J. 
Published: April 2021

ABSTRACT
Measurements have been made of the concentrations of potassium, chloride, calcium and magnesium, the conductivity and the membrane potential of single isolated fibres of the carpopodite extensor and flexor muscles of Carcinus maenas. Analyses of whole muscles gave the total concentration of the cations as 224 mM./kg. H2O, of which potassium accounted for 120 mM./kg. and sodium 54 mM./kg. Of the anion fraction chloride only accounted for 54 mM./kg. H2O. The analyses of the separated fibres were the same as for the whole muscle. The average specific resistance of the fibres is 56 Ω-cm. This represents a concentration of muscle ions of about 200 m.equiv./kg. and the electrolyte content of the muscle is not much more than a third of that of the blood. Between 72 and 91 % of the total muscle fibre cations are present in an ionized form. The average membrane potential is 58 mV. The ratios of the concentrations of potassium ions and chloride ions in the blood and muscle fibres suggest that these ions may be passively distributed across the membrane. The low concentration of sodium ions in the fibre probably indicates the operation of a ‘sodium pump’ as has been proposed for vertebrate muscles. The distribution of calcium and magnesium cannot be explained in simple terms. The correspondence between the equilibrium potentials for potassium and chloride ions and the membrane potential suggests that theory of ion distribution put forward by Boyle & Conway for frog’s sartorius muscle may also be applicable to Carcinus muscles.
Functioning of the Insect Ocellar Nerve
Authors: Hoyle G. 
Published: April 2021

ABSTRACT
The median ocellar nerve preparation of the locust Locusta migratoria has been re-investigated. The nerve contains six nerve fibres of which the two largest are 8 μ in diameter. The nerve fibres transmit propagated nerve impulses when the ocellus is illuminated or darkened. This disposes of the claim (Parry, 1947) that the ocellar nerve exerts an effect on the brain as the result of electrotonic spread from a depolarized region in the ocellus. The retinal potentials consist of a reduction of potential at the back of the ocellus on illumination and vice versa on darkening. This is the converse of the situation implicit in Parry’s exposition. Three kinds of nervous response are obtained from the ocellar nerve: an ‘on’-discharge, an ‘off’-discharge and a continuous dark-discharge. Corresponding discharges of nerve impulses are obtained from the circumoesophageal commissure. The ocellus must function principally as an indicator of changes in light intensity.
Osmoregulation and Ionic Regulation in Hydra
Authors: Lilly Sylvia J. 
Published: April 2021

ABSTRACT
Isolated tentacles of Hydra viridis were placed in solutions of sucrose of different known concentrations. In concentrations of sucrose greater than 0·04 M the tentacles shrank, and it was found that the ectoderm, endoderm, and enteron all contributed to this shrinkage. Both ectoderm and endoderm are highly permeable to water. Calculations suggest that the ectoderm cells are at least as permeable as various other cells which have been investigated by many workers. Shrinkage of the tentacle was very slight in 0·05 M sucrose, and no shrinkage occurred in 0·04 M sucrose. It is therefore suggested that the internal osmotic pressure is equivalent to that of 0·04−0·05 M sucrose. The uptake of the radioactive ions 24Na, 82Br, and 42K by Pelmatohydra oligactis has been investigated. All these ions are concentrated above the levels in the external medium. The relations between internal and external concentrations have been determined for sodium and bromide. The internal sodium concentration is maintained at a steady level with external concentrations varying from 5·4 m.moles/1. to approximately 0·20 m.mole/1. The internal bromide level has been shown to fall as the external bromide decreases from 2·5 to 0·05 m.mole/1. Higher external bromide concentrations could not be used as the animals were not healthy in solutions containing more than 0·25 g./l. NH4Br. The internal bromide is also shown to be depressed by the addition of chloride to the external solution. The results obtained indicate that the cells of Hydra are highly permeable to water, and also capable of maintaining an internal concentration of certain ions well above that of the external medium. This requires some form of regulation of water content and of ionic content. In the case of the latter it is not at present possible to say whether it is an active uptake of cations or anions.
The Breakdown of the Thoracic Gland in the Adult Insect, Rhodnius Prolixus
Authors: Wigglesworth V. B. 
Published: April 2021

ABSTRACT
The thoracic or ‘prothoracic’ glands of insects, which are the source of the growth and moulting hormone of the larval and pupal stages, degenerate and disappear soon after the final moult. In the adult Rhodnius the large nuclei of these glands are at an advanced stage of disintegration within 24 hr. of moulting, and at 48 hr. they have completely disappeared (Wigglesworth, 1952). The object of the present work was to study the physiological control of this breakdown.*
Comparative Studies of the Thyroid Function in Teleosts of Tropical and Temperate Habitats
Authors: Fortune P. Y. 
Published: April 2021

ABSTRACT
The presence of thyroid gland tissue in teleosts was first reported by Simon (1844), and later its structure was shown to consist of follicular units similar to those in the thyroid gland of higher vertebrates. The teleostean gland is not discrete but consists of numerous scattered follicles.
The Sources of Energy for Flight in Mosquitoes
Authors: Clements A. N. 
Published: April 2021

ABSTRACT
Reserve deposits of fat and glycogen are known to serve as sources of energy for flight in various insects. Among the Diptera only glycogen has been shown to serve this purpose ; the respiratory quotient of Drosophila in flight is close to 1·0 (Chadwick, 1947), and during flight glycogen disappears from the fat body but the deposits of fat are untouched (Wigglesworth, 1949). Tabanus has also been shown to use fat body glycogen during flight while apparently making no use of the fat deposits (Hocking, 1953).
The Wetting of Insect Cuticles by Water
Authors: Holdgate M. W. 
Published: April 2021

ABSTRACT
The water contact angles of insects show a wide range of variation, which is broadly correlated with surface roughness and with habitat. The contact angles of species inhabiting stored products or carrion are greatly modified by contamination. This produces large variations between apparently similar individuals. In terrestrial insects surface roughness increases the contact angles to very large apparent values. Detailed analyses of its effect have been made in the pupa of Tenebrio molitor and the adult Calliphora erythrocephala. In some aquatic insects surface roughness leads to a reduction in the contact angles; this has been studied in the nymph of Anax imperator. Prolonged immersion in water causes a lowering of the contact angles of all the insects examined, and the low angles of many aquatic species may therefore be the direct effect of their environment. In some aquatic species there is evidence of the active maintenance of a large contact angle during life. Changes in contact angle accompany processes of cuticle secretion and will occur at any moult if changes in roughness or habitat take place. The observed variations of surface properties can be explained without assuming any variation in the chemical composition of the cuticle surface. Wetting properties are of little value as indicators of cuticle surface composition. The biological aspects of insect surface properties are briefly discussed.
The Nerves and Muscles of Medusae
Authors: Horridge G. A. 
Published: April 2021

ABSTRACT
The co-ordination of the swimming movement (beat) and feeding response in Aequorea forskalea has been studied with particular attention to the pathways taken by the excitation. The rapid through-conducting system which co-ordinates the beat is sharply distinguished physiologically from the radial system which co-ordinates feeding. The spontaneous origin of the beat and its rapid marginal conduction are both inhibited while the radial muscle is contracting. Inhibition of this type has been observed in other genera of Hydromedusae
Ionic Regulation in the Muscle Fibres ofCarcinus Maenas
Authors: Shaw J. 
Published: April 2021

ABSTRACTThe electrolyte composition of the carpopodite extensor and flexor muscles of the chelae of Carcinus maenas living in diluted sea waters has been studied. The increase in water content of the muscles of crabs from 20% sea water corresponds to a maximum degree of swelling of 25 % of the initial weight. The resting membrane potential remains constant at 59 mV. over the whole range of blood concentrations studied. Chloride is lost from the fibres and its concentration in the muscle is always about one-tenth of that in the blood. Sodium ions are actively secreted from the muscles, and a steady state is reached when the concentration in the muscle is also about one-tenth that in the blood. The sodium and chloride concentrations in the muscle are approximately the same. The potassium concentration of the muscle falls as the blood is diluted, but the ratio of muscle potassium to blood potassium increases from 10 to about 20. Potassium appears to be actively retained in the muscle. The fall in concentration of muscle calcium and magnesium can be explained in terms of the swelling of the fibres alone and the fibre membrane is probably not permeable to these substances. The fibre is also probably impermeable to the larger part of the anion fraction. It is only sodium and potassium ions which are actively regulated and the result of these processes is that the muscle sodium balances the muscle chloride and the muscle potassium balances the impermeable anion fraction. It is suggested that on the extent to which the muscle cell can withstand blood dilution depends the degree to which it can resist swelling.
Further Studies of Gas-Filling in the Insect Tracheal System
Authors: Buck John , Keister Margaret 
Published: April 2021

ABSTRACT
In Sciara larvae exposed to total anoxia before moulting, all visible movement and all visible change in the content of the tracheal system cease. Moulting and tracheal gas-filing can be postponed at least hr. beyond normal time. In most third-stage larvae exposed to 0·3-0·75 % O2 before the third moult, the future fourth-stage tracheal system, which is present fully-formed in the body, fills with gas. This shows that although moulting invariably precedes gas-filling under normal circumstances it need not do so. In premoult larvae which have filled their trachea with gas upon exposure to 0·3-0·75 % O2, the tracheae fill again with liquid when the larvae are put back into atmospheric air. This reversal of gas-filling can be alternated with gas-filling several times in the same individual. The fact that in reversal of gas-filling an increase in pO2 promotes liquidfilling, whereas in moulted larvae it not only never leads to liquid-filling but actually accelerates gas-filling, indicates that some basic, but at least temporarily reversible physiological or chemical change occurs in the tracheae or in the metabolism of the peritracheal tissue, near the time of moulting. A partial explanation of the observed phenomena can be made in terms of a combination of active uptake and physical uptake of tracheal liquid. Evidence for the existence of both types of mechanism, separately, has been adduced by Wigglesworth in other material.
Seasonal Variations in the Growth Rate, Thyroid Gland Activity and Food Reserves of Brown Trout (Salmo Trutta Linn.)
Authors: Swift D. R. 
Published: April 2021

ABSTRACTSeasonal variations in the growth rate, food reserves and activity of the thyroid gland of hatchery-reared brown trout have been investigated. Two peaks of maximum growth rate were found, in spring and autumn. A marked depression of rate occurred during midsummer and winter. Fat which was laid down along the mesenteries and pyloric caecae was found to be the main food reserve. Glycogen was found in small quantities in the liver and muscle. The composition of the muscle and liver was constant except for an autumnal fall in the female liver glycogen level. The fat reserves reached a peak of 23 % by weight of the gut wall during July then fell to 5 % in autumn. Maturation of the gonads commenced in females in June and in males in July and was completed during October. The protein content of the ovary increased by 16%, and of the testis by 10%.The fat content of the ovary increased by 3 %. A new method is described for the determination of thyroid activity in fish using radioactive iodine. Peak thyroid activity was found to occur in midsummer.
The Water Relations of Earthworms
Authors: Roots Betty I. 
Published: April 2021

ABSTRACTSuitable media have been found for maintaining the activity of the nephridiostome cilia of two earthworm species for about 24 hr. at 18° C. or below. The nephridiostome cilia of Lumbricus terrestris are less resistant to hypotonic media, and more resistant to hypertonic media, than those of Allolobophora chlorotica. When the medium is suddenly diluted, the nephridiostome cilia of L. terrestris and A. chlorotica have a period of hyperactivity and/or increased amplitude of the beat followed by a return to normal activity. The temporary effect after a change to a hypertonic medium takes the form of decreased activity or inhibition. In hypotonic solutions, vesicles are formed on the marginal cells and later disappear provided the dilution has not been too great. A change in the osmotic concentration of the medium is responsible for the vesicles and the temporary effects on the cilia, whereas the inorganic ion concentration is responsible for the long-term effects. There is no axial gradient affecting the activity of the nephridiostome cilia in relation to the osmotic concentration of the medium. No differences were detected between garden and Lake Windermere specimens of A. chlorotica.
Facilitation in Sea Anemones. IV. The Quick Response of Calliactis Parasitica at High Temperatures
Authors: Ross D. M. 
Published: April 2021

ABSTRACT
Preceding papers of this series have dealt with the effects of a number of treatments on the quick responses of the sea anemones Calliactis parasitica and Metridium senile. Pantin’s (1935) analysis of the quick closing response in these animals showed that it is not normally elicited by single electrical stimuli, nor by stimuli following each other at intervals greater than about 3 sec. To get the closing response electrical stimuli must be given within a definite frequency range, at intervals of from about O-2-2-5 sec. at room temperatures. Between these limits, the closer the stimuli the bigger the response, with responses occurring, of course, only to the second and subsequent stimuli. This remarkable example of a facilitated response in which the response can only occur when facilitation has been set up, and in which the amount of facilitation determines the size of the response, raised many interesting problems. My work has centred on the approach of trying to set up experimental conditions in which single stimuli are effective, as this seemed a promising way of finding out more about the nature of this kind of facilitation.
The Eyes and the Photonegative Behaviour of Nephtys (Annelida, Polychaeta)
Authors: Clark R. B. 
Published: April 2021

ABSTRACT
The photoreceptors found in the Nephtyidae are: (a) Two pairs of vacuolated cells lying in pigment cups, with accessory cells, embedded in the posterior part of the supra-oesophageal ganglion.(b) One or two cells, which may or may not be vacuolated, on either side, lying a little anterior to the ganglion.(c) Undifferentiated epidermal cells surrounded by pigment granules may be photosensitive. There are both morphological and behavioural grounds for concluding that the prostomial eyes of Nephtys are homologous with the eyes of Nereis, and that they are involved in the same types of behaviour. The frequency with which Nephtys swims is, within limits, a linear function of the light intensity. Although the ganglionic eyes are directional receptors the worm does not orientate itself in a light beam; presumably the light reaching them is too diffuse. In the very small species N. cornuta, the eyes are close to the surface of the brain and the worm does orientate itself in a light beam. Swimming is an essential prelude to burrowing, and the brighter the light the more frequently the worm swims and the sooner it is buried. Activity in light can be inhibited by stimulating receptors on the dorsal surface of the animal by contact.
The Mechanical Properties of the Cell Surface
Authors: Mitchison J. M. 
Published: April 2021

ABSTRACT
Measurements were made with the cell elastimeter on the effect of a number of reagents and of changes in pH on the rigidity of the cell membrane of unfertilized sea-urchin eggs. The membrane rigidity was increased by dithiopropanol, thio-glycollate, chloracetophenone, a polyethanoxide and zinc ions. It was lowered by trypsin, cetyltrimethyl ammonium bromide and sodium dodecyl sulphate. Most of the other reagents, including respiratory inhibitors and calcium ions, had no effect. The membrane has a minimum rigidity at a pH of about 5-7.
Cellulose Digestion by the Silverfish Ctenolepisma Lineata*
Authors: Lasker Reuben , Giese Arthur C. 
Published: April 2021

ABSTRACT
It is the prevailing opinion to-day that the majority of species of animals which feed upon plants or plant products are unable to hydrolyse cellulose in spite of its abundance (Baldwin, 1952), depending instead upon the sugars, starches, fats and proteins present in the plant tissues. This implies the lack of a suitable alimentary enzyme, cellulase, or symbiotic gut micro-organisms which could perform that function. Study of cellulose digestion in animals is hampered by the difficulty of defining the role of the micro-organisms of the gut. If cellulolytic action is found in extract of tissues or in secretions of glands, the question remains whether or not this activity is attributable to micro-organisms; conversely, finding a cellulose-digesting microbe in the intestine of an animal does not prove conclusively its benefit to the animal.
Storage and Utilization of Reserves by the Garden Chafer, Phyllopertha Horticola L
Authors: Laughlin Roger 
Published: April 2021

ABSTRACT
Samples of all stages of Phyllopertha hortícola L. have been analysed for fat, total nitrogen and glycogen. Total nitrogen increases throughout the larval feeding period, while fat and glycogen are laid down mainly in the latter half. From November, when the third-instar larva goes into hibernation, until June, when the eggs have been matured and laid, no food is taken. Of the store of fat and glycogen in the hibernating larva at the beginning of the winter, half is used up by the time the adult emerges. The other half is used in the formation of eggs. Adult feeding provides energy for the post-oviposition activity period.