bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Effects of the Ionic Composition of the Extracellular Fluid On the Electrical Activity of the Cockroach Abdominal Nerve Cord
Authors: Treherne J. E.
Published: April 2021

Irrigation of abdominal ganglia of Periplaneta Americana with salines containing excess potassium ions resulted in the development of a reversible conduction block. Removal of portions of the cellular and fibrous nerve sheath produced an accelerated potassium depolarization as described by Twarog & Roeder (1956). Elevation of the cation concentrations to correspond to the extracellular levels resulted in delayed conduction block in desheathed preparations irrigated with highpotassium saline. At 70 mM./l. K the rate of depolarization was delayed to approximately half that of intact ganglia. At extremely high potassium concentrations this effect became relatively small. It is suggested that the enhanced rates of potassium depolarization obtained in desheathed preparations partly result from the changed ionic composition of the extracellular fluid resulting from the desheathing procedure. The possible additional factors involved in the desheathing procedure are discussed. 50 mM./l. acetylcholine had little effect on the synaptic transmission in intact terminal abdominal ganglia but caused rapid loss of conduction in desheathed preparations. Injection of equivalent amounts of acetylcholine beneath the nerve sheath did not cause rapid conduction block, and it is suggested that the effects of desheathing are not necessarily caused by the removal of a relatively impermeable superficial diffusion barrier.
Bifunctional Muscles in the Thorax of Grasshoppers
Authors: Wilson Donald M.
Published: April 2021

Recording electrical activity of certain dorso-ventral muscles in the thorax of grasshoppers has shown that the same muscles and (in at least one muscle) the same motor units may be used to move either the wings or the legs. The anatomical connexions are such that muscles which are antagonists with respect to the wings are synergists with respect to the legs, and vice versa. These muscles, which operate in a nearly perfectly repeating, fixed pattern during flight, show complete independence during manœuvres involving the legs and it is concluded that the flight pattern is not due to a fixed set of connexions between the motor neurons.
A Working Model for Demonstrating the Mosaic Theory of the Compound Eye
Authors: Altenburg Edgar
Published: April 2021

A working model of the compound eye can be constructed by the parallel arrangement of numerous tubes (e.g. straws) packed in a container. Lenses are not a necessary part of the model.

The defining power of the model depends upon the number of tubes per unit area—the greater their number, the more detailed is the image formed by the model.

The manner in which the model works would indicate that the image formed by the compound eye is a mosaic, or patchwork ; and that lenses take no primary part in image formation by a compound eye, but are merely accessory structures which bring about an increase in the amount of light that strikes the retina.
The Testis and Thyroid in a Hen-Feathered Silver-Grey Dorking Cock
Authors: Buchanan Gwynneth
Published: April 2021

A case is described of an apparently normal silver Dorking cock becoming hen-feathered.

The endocrine glands of this bird were examined, and the testes and thyroid found to be distinctly abnormal.

The testes showed large masses of “luteal” cells, encapsuled fibrosed masses, abnormal spermatogenesis and non-functioning tubules.

The thyroid showed myxoedematous and cystic conditions with an apparent attempt at compensation in the functioning tubules, and on the whole the appearance of an under-functioning gland.

The glands of two fertile Sebright bantams were examined.

The testes were normal, without “luteal” cells ; the thyroid was small, relatively rich in connective and poor in glandular tissue, with small secreting vesicles and poor blood supply, suggesting that the Sebright thyroid is subnormal in activity.

The evidence suggests that an under-functioning thyroid, either pathologically induced or apparently healthy, may be a controlling factor in hen-feathering, either by acting in combination with the gonad secretion, or by altering it.

The hypothesis is put forward that the thyroid and gonad act antagonistically in this respect; and a suggestion is made by which the condition of the plumage may be represented as the algebraic sum of the influence of the two glands.
The Energy-Sources in Ontogenesis
Authors: Needham Joseph
Published: April 2021

The uric acid content of the hen’s egg has been investigated from the fourth to the twentieth day of incubation. There is a period of intensive uric acid production from the seventh to the eleventh day. After that point the excretion of uric acid fails to keep pace with the growth and differentiation of the embryo. The point of maximum intensity of uric acid production occurs two days later than the point of maximum intensity in the production of urea. From the fourth to the seventh day more urea is present than uric acid, and more is excreted, but by the tenth day the adult relationship is attained, in which 95 per cent. of the total nitrogen excreted is uric acid. The maximum intensity of protein combustion is attained between the eighth and the ninth days. It is pointed out that this occurs midway between the periods when carbohydrate and fat are respectively the predominant energy-sources. The protein used as a source of energy belongs entirely to the coagulable fraction; ovomucoid is not employed for this purpose. The protein nitrogen lost by combustion during development amounts to 7.5 per cent. of the total protein nitrogen present at the beginning, and to 3.0 per cent. of the total foodstuff burnt. The R.Q. for each day of incubation has been calculated on the basis of chemical analyses of fat, protein, and carbohydrate, and agrees as well as can be expected at present with those experimentally determined by Bohr and Hasselbalch, and by Lussanna. Further evidence has been collected from the literature indicating that in embryogenesis there is a succession of sources of energy, carbohydrate preceding protein, and protein preceding fat. Injection experiments and other considerations lead to the conclusion that factors located in the embryo decide what the embryo shall make use of as a source of energy. It does not, for instance, combust protein because its supply of available carbohydrate has been exhausted.
A Comparison Between the Dissociation of the Haemocyanins of Helix and Crustacea
Authors: Hogben Lancelot T. , Pinhey Kathleen F.
Published: April 2021

The effect of increasing temperature upon the dissociation curve of Helix is similar qualitatively to that which has been recorded in the case of haemoglobin and crustacean haemocyanin. The value of Q per n gram molecules of oxygen is about 8000 calories. That is, it is of the same order of magnitude as the value for crustacean haemocyanin, but in all probability significantly less. The effect of increase of hydrogen-ion concentration upon the haemocyanin of Helix pomatia is remarkably slight as compared with its effect on crustacean haemocyanin. At low tensions no effect is detectable. Comparing the 50 per cent, and 75 per cent, saturation points, it is seen, that, as with crustacean haemocyanin, increasing hydrogen-ion concentration at first diminishes, but beyond a certain point increases, affinity for oxygen. The curves obtained on the acid side of this point are not identical in shape with the curves obtained on the alkaline side. The significance of this fact in relation to previous observations on crustacean haemo-cyanin, and to Rona and Ÿllpo’s experiments on haemoglobin, is discussed in the text. The behaviour of the haemocyanin of Helix as compared with that of crustacean haemocyanin in relation to the presence of neutral chlorides of the alkaline and alkaline earth metals is even more different. In alkaline medium, the addition of neutral chlorides to the serum depresses the dissociation curve ; at a point on the acid side of the critical pH referred to in section 2, addition of salts was not found to exert any detectable influence.
The Lethal Action of Soluble Metallic Salts on Fishes
Authors: Carpenter Kathleen E.
Published: April 2021

The work of several years on the fauna of streams polluted by lead-mining(1. 2, 3) has revealed the fact that the destruction of fish-life in such streams is neither a matter of starvation nor emigration for lack of food, nor of spawn-destruction, but is a direct consequence of the action of lead-salts in solution (probably as the sulphate) upon the fishes themselves. Further, experiments both in the field (using fish cages in the polluted streams) and in the laboratory (using filtrates of the flood waters and chemical solutions) have clearly demonstrated that one part of lead in three millions of water may be lethal to minnows, sticklebacks and trout. It seemed worth while, therefore, to investigate the physiological nature of the reaction in order to discover whether it followed the normal course of a toxic reaction.
The Filter-Feeding of Artemia
Authors: Reeve M. R.
Published: April 2021

Food ingestion in Artemia having been studied in some detail, attention was next directed towards certain aspects of the movement of food through and eventually out of the gut, in order to discover whether this process had any effect upon the method of feeding.
Caudal Fin and Body Movement in the Propulsion of Some Fish
Authors: Bainbridge Richard
Published: April 2021

Observations made on bream, goldfish and dace swimming in the ‘Fish Wheel’ apparatus are described. These include: An account of the complex changes in curvature of the caudal fin during different phases of the normal locomotory cycle. Measurements of this curvature and of the angles of attack associated with it are given. An account of changes in area of the caudal fin during the cycle of lateral oscillation. Detailed measurements of these changes, which may involve a 30 % increase in height or a 20 % increase in area, are given. An account of the varying speed of transverse movement of the caudal fin under various conditions and the relationship of this to the changes in area and amount of bending. Details of the way this transverse speed may be asymmetrically distributed relative to the axis of progression of the fish are given. An account of the extent of the lateral propulsive movements in other parts of the body. These are markedly different in the different species studied. Measurements of the wave length of this movement and of the rate of progression of the wave down the body are given. It is concluded that the fish has active control over the speed, the amount of bending and the area of the caudal fin during transverse movement. The bending of the fin and its changes in area are considered to be directed to the end of smoothing out and making more uniform what would otherwise be an intermittent thrust from the oscillating tail region. Some assessment is made of the proportion of the total thrust contributed by the caudal fin. This is found to vary considerably, according to the form of the lateral propulsive movements of the whole body, from a value of 45% for the bream to 84% for the dace.
The Action of Moulting Hormone and Juvenile Hormone at the Cellular Level in Rhodnius Prolixus
Authors: Wigglesworth V. B.
Published: April 2021

In the course of a discussion on the mode of action of growth hormones in insects (Wigglesworth, 1957 a) a preliminary account was given of the cytological changes brought about by the moulting hormone in certain selected tissues. Further work, with the use of improved methods, has substantiated many of these earlier results; others require revision.
Excretion in the Blood-Sucking Bug, Rhodnius Prolixus Stål
Authors: Maddrell S. H. P.
Published: April 2021

The mechanism underlying diuresis in Rhodnius has been investigated. An isolated preparation of the Malpighian tubules of a 5th-instar larva is described. The rate of secretion by such a preparation, isolated in a drop of haemolymph, is at first high but soon falls to a low level. It can be restored by the addition of haemolymph taken from an insect during diuresis. It has been shown that diuresis is promoted by some substance, presumably a neurohormone, which can be extracted from the posterior neurosecretory cells of the fused ganglionic mass situated in the mesothorax.
Studies On the Glomerular Filtration Rate of Rainbow Trout (Salmo Gairdneri)*
Authors: Holmes W. N. , Mcbean R. L.
Published: April 2021

Variations in the glomerular filtration rate (G.F.R.) and the renal tubular reabsorption of water are probably important factors in the homoiostatic mechanisms-associated with the euryhalinity of the rainbow trout (Salmo gairdneri). The observed reduction in urine flow after the adaptation of rainbow trout to sea water can be largely accounted for on the basis of the reduced G.F.R. Intraperitoneal injections of mammalian preparations of vasopressin, oxytocin and vasopressin/oxytocin into freshwater trout significantly increased the G.F.R. The intraperitoneal injection of aldosterone into freshwater fish had no detectable effect on G.F.R. The similar administration of corticosterone significantly reduced the G.F.R. to 73 % of the intact freshwater control value.
The Reaction of Fish to Moving Backgrounds
Authors: Harden Jones F. R.
Published: April 2021

An apparatus is described to study the response of fish to moving backgrounds. Observations were made on pike, three-spined sticklebacks, trout, perch and roach; cod, whiting, whiting-pout, smelt, herring, armed bullhead, lesser weaver, plaice, dabs, soles and dogfish. Pike followed a moving background equivalent to a water current of 0.03 cm./sec. Pike were the best and most consistent performers among the freshwater species, followed by the three-spined stickleback, trout, roach and perch. The marine species fell into two groups. The cod, whiting, whiting-pout, smelt, and herring responded to background movements equivalent to water currents of 1-2 cm./sec. The other fish failed to respond to movements equivalent to currents up to 24 cm./sec. and it is thought that this may have been due to contact with the bottom. The fish that orientated to a moving background also responded kinetically. Cod, whiting, and whiting-pout gained on the background (swam upstream) at rotational speeds equivalent to water currents less than 1 fish lengthlsec., but started to lag behind at speeds equivalent to currents faster than 1-2 L/sec., although the fish were shown to be capable of swimming fast enough to keep pace with the background. Herring gained on the background up to rotational speeds equivalent to water currents of 3-4 fish lengths/sec. The results are discussed in relation to the contranatant theory of fish migration.
Respiratory Regulation in Ephemera Simulans Walker and Hexagenia Limbata (Serville) (Ephemeroptera)
Authors: Eriksen Clyde H.
Published: April 2021

This study shows that Ephemera simulans and Hexagenia limbata are respiratory regulators and how it is that regulation is attained and maintained. Nymphs, 17-24 mm. in length, were acclimated in the laboratory at 13·0° C. for 24 hr. Oxygen consumption experiments employed the ‘closed-bottle’ technique and several modifications. When studied in bottles containing no substrate, both species appeared to be respiratory adjustors. Using ‘optimal substrates’ and a wide range of oxygen concentrations, both species proved to be respiratory regulators. As the oxygen concentration decreased, respiratory regulation was attained by initiating and increasing a flow of water past the body surfaces by the bailer action of beating gills. The volume passed was proportional to the number of gill beats which, in turn, was influenced by the size of the gills. The larger gills of Hexagenia beat at a slower rate to produce the same current as Ephemera and potentially they were capable of producing a significantly greater current and, hence, could regulate to a lower oxygen concentration.
An Electrophysiological Study of the Anatomical Relations of Two Giant Nerve Cells in Aplysia Depilans
Authors: Hughes G. M. , Tauc L.
Published: April 2021

Histological studies of the central nervous system of invertebrates using methylene-blue and silver-staining techniques, alone or in conjunction with degeneration experiments, have provided a considerable amount of information about neuronal pathways. The use of electrophysiological methods, however, makes it easier to trace the path of individual neurones over long distances and can be especially helpful in invertebrates where the path of an axon is complicated by its passage through the neuropiles. In addition, they may give some insight into the types of functional connexion which exist between neurones.
The Localization of Function in the Root of An Insect Segmental Nerve
Authors: Fielden Ann
Published: April 2021

The roots of the segmental nerves in nymphs of Anax imperator originate from separate dorsal and ventral tracts in the ganglionic neuropile. Axons forming the dorsal part of the nerve root can sometimes be traced to ganglion cells and tend to be large and thick-walled compared with the ventral axons which are smaller and thin-walled. In the roots of the fifth nerves of the last ganglion the two parts can be separated by dissection. Recording from each part under various conditions of stimulation shows that sensory activity occurs predominantly in the ventral part of the nerve root whilst motor spikes are recorded almost entirely from the dorsal part. It is concluded that there is a functional localization of motor and sensory fibres in the root of an insect nerve comparable to that in the dorsal and ventral roots of vertebrate nerves.
Organic Constituents of the Seminal Plasma ofBalanus Balanus
Authors: Barnes H.
Published: April 2021

The seminal plasma of Balanus balanus has been analysed for a number of organic substances including total nitrogen, protein, urea, protein-bound hexose, hexosamine, fucose, ‘sialic acid’, glycogen, and RNA. The material was separated into soluble and insoluble fractions by precipitation with ethanol. A large part of the ethanol-soluble material is inorganic salts and glycine; it contains a small quantity of protein-like material which on hydrolysis yields largely glycine and glutamic acid. The alcohol-precipitated material contains protein, protein-bound hexose, hexosamine, lipids, and RNA. Glycogen, fucose, and ‘sialic acid’ are absent. It is suggested that the plasma contains glycoproteins of a mucoid nature: the absence of both fucose and ‘sialic acid’ suggests that the mucoid may be of a relatively simple character. Attention is drawn to the similarity of this seminal plasma, which is produced in the absence of accessory male organs, to that of higher animals.
Sensitivity of Neurones inAplysiato Temporal Pattern of Arriving Impulses*
Authors: Segundo J. P. , Moore G. P. , Stensaas L. J. , Bullock T. H.
Published: April 2021

Experiments were carried out on the isolated ganglia of Aplysia californica to discover whether the precise timing (i.e. the interspike interval distribution and sequence) of a group of spikes entering a neuronal system at a given mean frequency constitutes a variable that is significant in the control of its output. The input consisted of stimulation bursts with different timings but identical mean frequencies applied to one or more afferent trunks. The output (EPSPs or spikes) was monitored with an intracellular micro-electrode placed in the giant cell. Changes in the timing of the input produce definite changes in the magnitude of the output, both in terms of depolarization induced and of spikes evoked. Because of the critical nature of the spike firing threshold, a consistent small increment in depolarization due to favourable timing can be functionally important in the vicinity of the firing level. The following properties contribute to timing-dependence : (i) Temporal summation of successive EPSPs. (ii) Interaction. Each EPSP is characteristically augmented or, more frequently, decreased by those preceding it; linear summation is a special case. The modification in general cannot be predicted from the excitability cycle after one EPSP; interactions between EPSPs of different origins are often irreciprocal; sequence of heterologous inputs is influential, (iii) Post-spike excitability. Responsiveness changes which follow a post-synaptic spike depend on whether it is preceded by others, on their number and timing. Nerve cells were thus found to exhibit a sensitivity to timing that issued from elementary functional attributes. Such sensitivity to timing would be biologically advantageous, especially in areas of sensory convergence, for it provides an additional coding parameter complementing mean frequency modulation. It is still too early to decide whether or not this mechanism is actually important in natural operation, though it appears likely.
Temperature Relationships of the Locomotor Rhythm ofCarcinus
Authors: Naylor E.
Published: April 2021

The locomotor rhythm of Carcinus maenas was shown to be relatively similar at 10°, 15°, 20° and 25° C., but it was shown to be modified by changes in temperature. A fall of about 5 − 10° C. just before the onset of activity usually advanced and enhanced the initial peak of activity, whilst a rise of the same magnitude usually delayed and partly suppressed the initial peak, each without affecting the basic rhythm. A fall in temperature of about 10° C. or more between activity peaks usually initiated transient outbursts of activity, again without affecting the normal rhythm. Chilling to 4° C. for more than 6 hr., irrespective of the time of onset of chilling, resulted in a rephasing of the rhythm with the initial outburst occurring immediately on return to room temperature. In Carcinus from non-tidal docks chilling resulted in a change from the normal approximately nocturnal rhythm to an overt tidal rhythm, but in Carcinus from the virtually tideless Mediterranean the character of the normal nocturnal rhythm was unaffected by chilling.
Transpiration inPodura AquaticaL. (Collembola, Isotomidae) and the Wetting Properties of Its Cuticle
Authors: Noble-Nesbitt J.
Published: April 2021

In the collembolan, Podura aquatica, transpiration through the cuticle is high at all relative humidities. Above 90% relative humidity, cuticular permeability is abnormally high but no adequate explanation of this can be given. Transpiration through the cuticle is high at all temperatures and there is no evidence of a critical temperature over the range 17-29° C. Abrasion increases the transpiration rate, and at least partial recovery occurs within the instar. Moulting fully restores the transpiration rate to the normal level. The hydrofuge nature of the cuticle strongly suggests the presence of an orientated lipid monolayer on its surface. Strong wax solvents render the cuticle wettable, whereas treatment with water under reduced pressure does not. Consideration of the fine structure suggests that the hydrofuge layer is discontinuous and that it occurs on the tips of the minor tubercles. This is compatible with an overall high transpiration rate. The occurrence of hydrophil areas of cuticle is correlated with a smooth cuticular surface. The biological effects of the hydrofuge and hydrophil areas in the life of the insect are discussed.
A Site of Water and Ionic Exchange with the Medium inPodura AquaticaL. (Collembola, Isotomidae)
Authors: Noble-Nesbitt J.
Published: April 2021

In the collembolan Podura aquatica L., uptake of water occurs both via the mouth and across the ventral tube vesicles. Drinking is important in water-stress situations and when the haemolymph pressure is too low for eversion of the vesicles. Everted vesicles alone are sufficient for recovery from partial desiccation. Experiments in which insects with their mouths or ventral tubes blocked were exposed to a medium containing 24Na indicated that most of the exchange of sodium between insect and medium occurred over the ventral tube vesicles, and that this exchange was rapid. In experiments using 42K, no measurable exchange occurred between the insect and the medium.
Studies On the Myoneural Physiology of Echinodermata
Authors: Boltt R. E. , Ewer D. W.
Published: April 2021

The lantern retractor muscle of Parechinus angulosus responds to light stimulation by a rapid contraction which is followed by a slower increase in tension. The details of these contractions vary from preparation to preparation. With very brief light exposures only the quick response is shown, while with prolonged light stimulation rhythmical activity develops after a minute or more. Exposure of a contracting preparation to the light of a mercury vapour lamp causes a slight fall in tone. This is not due to the ultra-violet component of this light. Responses to repeated light pulses may result in simple summation or the response to the first pulse may be markedly greater than those which follow. In preparations which show this latter effect, there is evidence for an inhibitory phenomenon which persists for about 30 sec. With paired stimuli the response to the second stimulus may show an initial depression which reaches a maximum at an interval of about 10 sec., then a recovery and finally a second depression of response which is maximal when the interval between stimuli is about 5 min. There is evidence that stimulation of the comminator muscles may result in loss of tone of the lantern retractor muscles. A provisional hypothesis to explain these effects is presented.
Studies On Crop Function in the Cockroach (Periplaneta AmericanaL.)
Authors: Davey K. G. , Treherne J. E.
Published: April 2021

The structure and mode of action of the proventriculus are described. X-ray photographs have shown that as the crop empties the decrease in volume of the fluid is partially compensated for by the swallowing of air. The effects of various factors upon the rate of crop-emptying have been studied using solutions of different osmotic pressures. Changes in viscosity, effected by the addition of methyl cellulose, produce only a minor reduction in crop-emptying. The frequency of opening of the proventricular valve is not proportional to the rate of crop-emptying over the whole range of concentrations used, and it is assumed that changes in other parameters must affect the process.
Rectal Absorption in the Desert Locust, Schistocerca Gregaria Forskål
Authors: Water I. , Phillips J. E.
Published: April 2021

The histology of the rectum of Schistocerca gregaria is described. A method is described whereby net absorption of water from the rectum (in situ, isolated by ligation) can be measured. Water is actively absorbed from the lumen of the rectum against an osmotic gradient and in the absence of a significant net flux of solute. The maximum osmotic gradient developed is 2-3 times greater in locusts supplied with hypertonic saline than in locusts supplied with tap water. This indicates some ability to regulate water absorption in relation to requirement. The ionic concentration of rectal fluid and the rate of salt absorption from the lumen have little effect on the maximum osmotic gradient developed across the rectal wall. Possible mechanisms of active absorption of water are discussed.
Excretion in the Blood-Sucking Bug, Rhodnius Prolixus Stål: II. The Normal Course of Diuresis and the Effect of Temperature
Authors: Maddrell S. H. P.
Published: April 2021

The course of diuresis in Rhodnius is described and interpreted in terms of the underlying mechanism. The rapid onset of diuresis is attributable to the prompt release of the diuretic hormone into the haemolymph and to an acceleration of the circulation of the haemolymph caused by peristaltic movements of the mid-gut. Diuresis proceeds at a surprisingly constant rate. This is shown to be a reflexion of the fact that the concentration of the diuretic hormone in the haemolymph at this time is always higher than that which causes the maximum response by the Malpighian tubules. The diuretic hormone is quickly destroyed by the activity of the Malpighian tubules and possibly other tissues. Consequently, the extent of diuresis is controlled by the length of time during which diuretic hormone is released into the haemolymph. Excretion is very sensitive to changes in temperature; both the rate of excretion and the composition of the urine are affected.
The Lift-Control Reaction of Flying Locusts
Authors: Gettrup Erik , Wilson Donald Melvin
Published: April 2021

Angle of attack of a distal wing segment was estimated for forewings and hind-wings of locusts during constant lift at different body angles. At the middle of the downstroke the forewing angle of attack remained nearly constant, but the hindwing angle varied with the body angle. The results are consistent with earlier electro-physiological findings and emphasize that the twist parameter does not contribute by equal amounts to the mean wing twisting of the two pairs of wings. A qualitative model of the constant-lift reaction includes a factor for simultaneous correction of body pitch.
Rectal Absorption in the Desert Locust,Schistocerca GregariaForskål: III. The Nature of the Excretory Process*
Authors: Phillips J. E.
Published: April 2021

The physiology of the excretory system and its role in salt and water balance have been studied in the desert locust, Schistocerca gregaria. Collections and analyses were made of hindgut fluid (derived from the Malpighian tubules) and rectal fluid from locusts kept under various dietary régimes. In starved locusts supplied with tap water very little fluid accumulates in the rectum, the output of the Malpighian tubules being almost completely reabsorbed. Relatively more salt than water is reabsorbed with the result that the rectal fluid, attains a lower ionic concentration but higher osmotic pressure than the haemolymph. No fluid is voided. In starved locusts supplied with hypertonic saline the rectum is distended with fluid which has an osmotic pressure and ionic concentration considerably above that of the haemolymph. Very little fluid is voided. Substantial elimination of fluid from the rectum occurs only in fed locusts, in association with the voiding of faeces. These results are discussed in relation to the mechanism of osmotic and ionic regulation.
Some Aspects of Electrolyte Excretion in the Green Turtle, Chelonia Mydas Mydas
Authors: Holmes W. N. , McBean R. L.
Published: April 2021

The ‘salt gland’ appears to be the predominant route of sodium and potassium excretion in the marine turtle Chelonia mydas mydas. The kidney of the marine turtle is probably not capable of maintaining a positive water balance in the face of the electrolyte loads presented by sea water and food. Treatment with amphenone reduced the sodium and potassium excretion of fed and saline-loaded marine turtles. The administration of corticosterone partially corrected this reduction. Thus the excretion of electrolytes by the ‘salt gland ‘appears to be, at least partly, dependent upon a fully functional adrenal cortex. The significance of the ingestion of sea water by marine turtles is discussed in relation to the excretion of the large amount of potassium contained in their food.
Diffusion in Insect Wing Muscle, the Most Active Tissue Known
Authors: Weis-Fogh Torkel
Published: April 2021

The tracheal system of insect wing muscle is so dense that between 10−1 and 10−3 of any cut area is occupied by air tubes. In most cases, air tube diffusion of O2 and CO2 through the muscle is therefore several thousand times quicker than diffusion in the liquid phase. In large insects the primary tracheal supply must be strongly ventilated while diffusion is sufficient in the remaining part of the air tubes, even at the highest metabolic rates encountered in any insect. The tracheoles represent the main site of exchange between the gaseous and the liquid phase while the tracheae are of little significance in this respect. The fibres cannot exceed about 20 μ in diameter unless the tracheoles indent the surface and become ‘internal’. Muscular pumping of air and blood due to shortening is of little importance for the exchange of gases but of major importance for the supply with fuel for combustion. However, the large fibre diameters and the tidal nature of the pumping necessitates a very high concentration of fuel in the haemolymph. The high concentration of trehalose in insect blood is considered to be an essential adaptation to flapping flight. The transport by diffusion of O2 and CO2 was followed in detail in a number of concrete examples in the gaseous as well as in the liquid phase. Within a safety factor of 2–3, the rate of transport was always found to be adequate. There is no reason to suggest other mechanisms than a simple, normal diflfusion.
Locomotory Movements of the Hind Limbs in Rabbits After Isolation of the Lumbosacral Cord
Authors: Cate J. Ten
Published: April 2021

In my earlier experiments with spinal cats (1962) I established that the isolated lumbosacral cord is able to co-ordinate walking movements of the hind limbs. In cats this part of the cord possesses a high degree of autonomy. It seemed interesting to know whether in rabbits the isolated lumbosacral cord is also able to maintain these functions. It was especially important to establish whether the spinal rabbit can carry out the typical jumping movements with hind limbs, which serve, as is well known, in the act of progression in normal conditions.
The Reproductive Biology of the Rabbit Flea Spilopsyllus Cuniculi (Dale) and the Dependence of this Species Upon the Breeding of Its Host
Authors: Mead-Briggs A. R.
Published: April 2021

Unlike any other species of flea which has been cultured successfully Spilopsyllus cuniculi (Dale) is entirely dependent for its own reproduction upon its host becoming pregnant. The ovaries of fleas kept on male or non-pregnant female rabbits remain immature whereas those on a pregnant host are mature at the time of parturition. Vitellogenesis commences at a critical point approximately 7 days pre-partum, irrespective of how long the fleas have been on the host. It is postulated that a factor required by the flea for ovarian development is only available during the final week of pregnancy, and not at all in male or non-pregnant rabbits. The factor disappears from the adult after parturition but is present in her nestlings for at least 7 days. Most fleas desert the adult doe shortly after the young are born and enter her nest, where copulation and oviposition occur. The factor does not act solely as a trigger initiating in the flea developmental processes which then continue in its absence; ovarian regression occurs among maturing fleas transferred to hosts that do not supply the factor. The processes of vitellogenesis, not those of oogenesis, fail in the absence of the factor. It is suggested that the ‘yolk-forming hormone’ normally secreted by the corpus allatum of the adult insect may only be produced by rabbit fleas when they can obtain the postulated factor. Variations in the quantity of this factor available to fleas on different hosts could explain the observed variations in ovarian activity. Some parallels between the factor and steroid hormone levels in the host’s blood are discussed.
Factors Influencing Submergence and the Heart Rate in the Frog
Authors: Jones D. R. , Shelton G.
Published: April 2021

The ability of the frog to remain submerged declines as the oxygen concentration in the water falls or the carbon dioxide content rises. The critical oxygen concentration appears to be about 5 mg./l. and the critical carbon dioxide concentration 100 mg./l. at temperatures around 10° C. Submergence results in a decrease in heart rate which develops over a period of 15-30 min. but which disappears immediately the animal surfaces and breathes. The bradycardia is accentuated by oxygen lack or carbon dioxide excess. During submergence the heart is influenced by two main factors, the shortage of oxygen and the cessation of breathing movements, both of which contribute to the decrease in rate. The former can still affect rate after vagotomy. The connexion between breathing and heart rate is dependent on the nervous system, though the detailed pathway is not worked out.
The Role of Lipid in Adult Development and Flight-Muscle Metabolism in Hyalophora Cecropia*
Authors: Domroese Kenneth A. , Gilbert Lawrence I.
Published: April 2021

Changes in total lipid and R.Q. show that female pupae of H. cecropia begin to catabolize lipid early in adult development. In males there is a conservation of lipid during adult development resulting in the male moth having about three times the lipid content of the female. In the adult moth both sexes utilize lipid as the major energy source. Lipid is the available substrate as well as the preferred substrate in flight-muscle metabolism in male moths. Flight-muscle homogenates show greater oxidative activity with fatty acids and citric acid cycle intermediates than with glucose or glycolytic intermediates, indicating that carbohydrate pathways are not prominent. A fatty acid oxidizing system has been identified in flight muscle which requires ATP, magnesium and a citric acid cycle intermediate for optimum activity. Experiments with radiotracers and metabolic inhibitors reveal that fatty acid oxidation in flight muscle proceeds via the citric acid cycle and the cytochrome chain. Active fatty acid activating enzymes are present in flight muscle, and fatty acid oxidation in H. cecropia is discussed in relation to vertebrate and other invertebrate systems.
Sodium and Chloride Balance in the Prawn, Palaemonetes Varians
Authors: Potts W. T. W. , Parry Gwyneth
Published: April 2021

The exchanges of sodium and bromide (for chloride) ions between the brackish-water prawn Palaemonetes varians and its environment are described. In an isosmotic medium the exchange of sodium and chloride ions takes place by passive diffusion. In full-strength sea water sodium ions are actively removed extrarenally, the potential difference produced by the active extrusion of sodium ions maintaining the chloride ions in passive equilibrium. There is some evidence of an increased flux of ions in hyperosmotic sea water associated with water-swallowing to obtain water for water balance. In 2 % sea water chloride ions are actively absorbed, the potential produced by this active uptake helping to maintain sodium balance ; but some active sodium uptake also occurs. In salinities below 2% uptake of ions declines and the animals can no longer maintain equilibrium.
Sperm Penetration of the Zona Pellucida of the Pig Egg
Authors: Dickmann Z. , Dziuk P. J.
Published: April 2021

Pig eggs were examined with the ordinary and phase-contrast microscope in search for clues about the process of sperm penetration of the zona pellucida. The following observations were made, (i) The zona pellucida consists of three concentric layers—the inner-zona, the middle-zona, and the outer-zona, (ii) The fertilizing spermatozoon makes a narrow slit in the zona by penetrating through it. The slit has a particular shape referred to as ‘the penetration curve ‘. (iii) Extra spermatozoa (i.e. spermatozoa other than the fertilizing spermatozoon) enter the zona and follow a course very similar to that of the fertilizing spermatozoon, but they can penetrate it only as far as the middle-zona. Extra spermatozoa have not been observed in the inner-zona, indicating that in this layer the ‘zona reaction’ is normally absolute, (iv) A filament extending from the apex of the sperm head has been observed in spermatozoa embedded in the zona. It is suggested that the sperm path through the zona is determined by this filament, which is therefore termed the sperm-penetration filament (SPF). On the basis of these observations the following sequence of events in the passage of a spermatozoon through the zona is suggested. First, the spermatozoon attaches to the zona; it then ejects into the zona the SPF. The SPF, in turn, guides the spermatozoon on its curved course through the zona.
Water Balance in Corixa Dentipes (Thoms.) (Hemiptera, Heteroptera)
Authors: Staddon B. W.
Published: April 2021

The water balance in Corixa dentipes (Thoms.) has been investigated under conditions of starvation in de-ionized water. The rectal fluid was found to contain almost sufficient ammonium bicarbonate to account for the total osmotic pressure. It was invariably strongly hypotonic to the haemolymph. The water output, as estimated by measuring the ammonia output and ammonia concentration of the rectal fluid, was shown to be appreciable but no connexion was found between the output of ammonia and of water. Adults were shown to gain water by the mouth and some evidence was obtained that the cuticle may be an important route of water intake.
Detour Experiments With Octopuses
Authors: Wells M. J.
Published: April 2021

Octopuses will make detours to get at prey seen through a transparent barrier, even though the detours carry them temporarily out of sight of the prey. The possibility of non-visual intermediate cues can be eliminated experimentally. Eight out of 29 octopuses tested made a successful detour at the first trial. The remainder had to be led through the maze by means of a crab on a string on one or more occasions before they did it spontaneously. Once having completed a successful detour down a passage to get into a feeding compartment to the side of the corridor, an octopus rarely failed in subsequent trials, whether making a detour to right or to left. Eleven unoperated control animals, each tested 20 times, totalled only 10 errors, by going into the feeding compartment on the wrong side of the corridor; they failed to make a detour only 13 times in 220 trials. Performance nevertheless showed some improvement with practice. The number of seconds spent attacking through the wall of the feeding compartment before entering the corridor and the number of abortive entries into the corridor both decreased as trials continued. Removal of the statocysts did not stop the high proportion of correct responses. In 39 trials four animals made 6 errors, 3 of them attributable to unilateral blinding of one of the animals (see below). Blinding the animals in one eye led to systematic errors in detours towards the unblinded side. In 63 trials towards the unblinded side, four octopuses made 16 errors and failed to complete the detour 28 times. In 63 trials towards the blind side there were only 4 errors and 9 failures. It is concluded that orientation in detours is maintained by keeping close visual contact with the wall separating the octopus from its prey. The experimental results indicate that octopuses do not take bodily position into account in learning to make detours. Animals trained to make a detour to one side only performed faultlessly when first required to make a detour in the other direction; there is no indication that octopuses are guided by external cues in these experiments. These results are discussed in relation to the organization of motor and learning systems in animals generally. Creatures with hydrostatic skeletons and flexible bodies must of necessity have a decentralized motor control system, and this has important consequences on their learned behaviour.
Experiments on Substrate Selection byCorophium Volutator(Pallas): Depth Selection and Population Density
Authors: Meadows P. S.
Published: April 2021

An apparatus is described for testing substrate-depth preferences of Corophium volutator (Pallas). Corophium burrow in mud whatever its depth, if only one depth of mud is available. If presented with muds of different depths, more animals burrow in the deeper muds. Very shallow muds, of 0·5 cm. depth, are particularly avoided. Although preferring deeper muds, animals are persuaded to burrow in shallow muds when the surface population density in the deeper muds is at a high level (> 0·1 animals/cm.2). This would be explained by a pattern of territorial behaviour which shows itself only at relatively high population densities. Analysis of the distribution of animals at low densities indicates some tendency towards gregariousness. Because of the periodic tendency for animals to vacate their burrows and burrow elsewhere, more than 50% of burrows at very low surface-population densities (ca. 0·01 animals/cm.2) may be unoccupied. Larger animals tend to be found in deeper muds. This would lead to substrate depth influencing the age structure of populations in the field. Limitations imposed by the shape and size of the burrow, rather than animal size in itself, probably explain why animals avoid shallow muds and why larger animals are found in relatively deeper muds.
Responses of Nymphon Gracile (Pycnogonida) to Pressure Cycles of Tidal Frequency
Authors: Morgan Elfed , Nelson-Smith A. , Knight-Jones E. W.
Published: April 2021

The responses of Nymphon gracile to changes in hydrostatic pressure are described. (M, the unit of pressure used here, denotes 1 metre sea water.) A sudden increase in pressure tended to inhibit swimming, while a reduction promoted it, a response opposite in sense to that normally associated with depthregulation. Nymphon showed no adaptive response to cyclical pressure changes similar to those produced by onshore waves. Pressure changes of similar range (1M) but with a 2 sec. period usually induced swimming in previously sluggish individuals. Pressure cycles of 8M range and periods ranging from 14 to 160 min. evoked a depth-regulatory type of response in several individuals, but the majority responded in the opposite way. Nymphon responded to cyclical pressure changes of approximately tidal range (8M) and frequency, by swimming most actively during the late ebb or low water of the artificial cycles. The data of Fage (1932) support the hypothesis that Nymphon swims most often when stimulated by decreasing pressure as the tide ebbs.
The Control of Emergence and Metabolism by External Osmotic Pressure and the Role of Free Glycerol in Developing Cysts of Artemia Salina
Authors: Clegg James S.
Published: April 2021

The effects of external osmotic pressure on the rates of development and emergence, respiration, and on changes in glycogen, glycerol, and trehalose concentrations have been studied in cysts of Artemia salina. The only measured effect of external osmotic pressures less than 30 atm. on emergence and development is to determine the time required for the embryo to emerge from the cyst. Above this value the onset, rate, and final percent of emergence decrease. No emergence occurs at osmotic pressures greater than about 65 atm. The oxygen consumption decreases with increased osmotic pressure, and is negligible at about 65 atm. Several lines of evidence show that trehalose is the respiratory substrate, that most of the trehalose present in the dormant embryo is converted to glycogen and glycerol during development, and that the direction and extent of these conversions are controlled by the external osmotic pressure. Glycerol appears to be present in at least two distinct locations in the cyst: within the embryo, and between the embryo and shell. Glycerol in the latter location is released into the medium at the time of emergence; the embryonic glycerol is rapidly metabolized after emergence. The physiological significance of glycerol and trehalose in the emergence process is discussed.
Tension At The Surface of Sea-Urchin Egg: A Critical Examination Of Cole’s Experiment
Authors: Yoneda Mitsuki
Published: April 2021

The sea-urchin egg can be deformed by external force, and on removing the force it tends to round up. Assuming that the inner protoplasm is liquid, such a return to sphericity must be due to a force working at or near the surface of the egg. The surface force, or the tension at the surface, as referred to by Harvey, has been measured by several methods (Vlès, 1926; Harvey, 1931; Cole, 1932; Cole & Michaelis, 1932; Sichel & Burton, 1936; Norris, 1939). Most of them were reviewed by Harvey & Danielli (1938). Among these workers, however, Cole alone provided information which has been accepted as a proof that the cortex is elastic.