bluuebunny/crossref_metadata_2025 huggingface dataset:
Hormonal Control of Sexual Maturity in Octopus
Authors: Wells M. J. , Wells J.
Published: April 2021

Gonad and body weight records have been collected for 487 individual octopuses over a period of 3 years. In the size range used for experiments (200–1000 g.), the ovary is always immature in control animals, and constitutes only about 1/500th of the total body weight. The testis is rather larger, generally ripe, and forms about 1/100th of the body weight, increasing somewhat relative to the size of the body over the range considered. Following optic nerve section, or removal of certain parts of the supraoesophageal lobes, the gonads enlarge. In females the ovary enlarges from 1/500th to as much as 1 /5th of the total body weight within 5 weeks of operation and this may be followed by laying of fertile eggs that are brooded in a normal manner. In males where the testis is generally mature before operation the enlargement produced is only of the order of 50%. Enlargement of testis or ovary is always accompanied by enlargement of one or both of the optic glands, and operational treatments that normally cause enlargement of the gonad are ineffective if the optic glands are first removed. The optic glands are innervated from the subpedunculate/dorsal basal area in the hind part of the supraoesophageal brain mass. Lesions in this area, or severance of the nerve tracts running along the sides of the brain from it to the optic glands, cause these and the gonads to enlarge. Unilateral central lesions or optic nerve section cause optic gland enlargement on the operated side only, but appear to be as effective in determining gonad enlargement as bilateral treatments. It is concluded that maturation of the gonad is determined by secretion from the optic glands which is normally held in check by an inhibitory nerve supply from the subpedunculate/dorsal basal lobe area. The action of this region is in turn dependent upon the integrity of the optic nerves and thus, presumably, upon light. This system in cephalopods is compared with analogous systems regulating sexual maturity in arthropods and vertebrates.
The Absorption of Sodium Ions by the Crayfish, Astacus Pallipes Lereboullet
Authors: Shaw J.
Published: April 2021

The effects of external and internal sodium concentrations.on the uptake of sodium ions by the crayfish, Astacus pallipes, has been studied. The normal sodium influx, measured with 24Na, from 0-3 mM./l. NaCl solution is 1-5 /xM./io g. body weight/hr. The rate of loss of sodium to de-ionized water has roughly the same value. Net loss of sodium reduces the external sodium concentration required for sodium balance. The minimum equilibrium concentration is about 0 04 mM./l. NaCl. The relation between the external sodium concentration and the sodium influx is non-linear. The influx has a maximum of about 10μM./IO g./hr. at an external concentration of approx. 1 mM./l. The 24Na influx is a true measure of the sodium uptake rate at low external concentrations. At higher concentrations the influx may exceed the uptake rate by some 20%. Net loss of sodium increases the influx by three to five times. Loss of 5-10% of the total internal sodium increases the influx from the normal to the maximum level. A 1 % change has a significant effect on the influx. Changes in the internal sodium content reflect changes of the blood sodium concentration. A scheme is suggested whereby the external and internal sodium concentrations interact together on the influx to produce a self-regulating system which maintains the animal in sodium balance.
Salt and Water Balance in the East African Fresh-Water Crab, Potamon Niloticus (M. Edw.)
Authors: Shaw J.
Published: April 2021

The mechanisms of salt and water balance in the East African fresh-water crab, Potamon niloticus, have been investigated. The freezing-point depression of the blood is equivalent to that of a 271 mM./l. NaCl solution. The animals cannot survive in solutions more concentrated than 75% sea water. Above the normal blood concentration, the blood osmotic pressure follows that of the medium. The urine is iso-osmotic with the blood and is produced at a very slow rate. The potassium content is only half that of the blood. The animal loses sodium at a rate of 8 µM./10 g./hr. mainly through the body surface. Potassium loss occurs at one-sixteenth of this rate. Sodium balance can be maintained at a minimum external concentration of 0-05 mM./l. Potassium requires a concentration of 0·07 mM./l. Active absorption of both sodium and potassium occurs. The rate of uptake of sodium depends on the extent of previous sodium loss. The rate of sodium uptake may be affected by such environmental factors as the salt content of the water, temperature and oxygen tension. The normal oxygen consumption rate is 0-72 mg./io g./hr. A minimum of 2-3 % is used in doing osmotic work to maintain salt balance. The salt and water balance in Potamon is discussed in relation to the adaptation of the Crustacea to fresh water. The importance of permeability changes is stressed.
The Effects of High Temperatures on Roach (Rutilus Rutilus)
Authors: Cocking Anthony W.
Published: April 2021

The temperature at which 50 % of a sample of roach (Rutilus rutilus) die within a week cannot be raised above 33-5° C. by raising the acclimatization temperature. The roach is about as eurythermal as the yellow perch (Perea flavescens). The mean asphyxial concentration of oxygen at 30 and 32° C. is approximately o-8 mg./l. Median survival time at any lethal temperature increases with increase in acclimatization temperature; survival time for any acclimatization temperature decreases as test temperature increases; the temperature at which 50 % of a sample die within a week rises by about i° C. for each 30 C. rise in acclimatization temperature. The behaviour, on transfer to higher temperatures, depends on the acclimatization temperature and the size of the jump in temperature and can be divided into five characteristic stages. Dying fish develop a black pattern ; myotomie swimming muscles die first and opercular muscles last. The heart was still beating when the fish were opened but the gall bladder was abnormal.
Two Components from the Compound eye of the Crayfish*
Authors: Naka K. , Kuwabara M.
Published: April 2021

The aim of the present investigation was to confirm the results obtained in the previous paper with the aid of the microelectrode. It is concluded that the two components, H-I and H-II, originate from different structures in the receptor layer. It is shown that a difference in the steady potential ranging from 10 to 50 mV is maintained across the basement membrane.
Respiratory Reflexes in the Dogfish
Authors: Satchell G. H.
Published: April 2021

Inflation of the pharynx of a dogfish causes an inhibition of respiration manifested as a reduction in rate and amplitude. Tetanic stimulation of the central end of a cut branchial nerve also inhibits respiration. These inhibitory responses differ in their greater regularity and duration from the transient inhibition arising from stimulation elsewhere in the body. Both normal respiration and inflation cause the discharge of receptors whose impulses pass up the vagus nerve. The pattern of firing of these receptors during an inflation corresponds to the pattern, of inhibition. Brief inflations are more effective in securing inhibition if they arrive at a time when the receptors are not being caused to fire by a normal inspiration. Cutting the branchial branches of the IXth and Xth nerves eliminates the pause between successive respirations and increases the respiratory rate. These pauses can be made to reappear by periodically stimulating the central end of a cut branchial nerve. Section of the brain between the medulla and the mesencephalon increases the sensitivity to inflation. Inhibitory afferents run in all branchial branches of the IXth and Xth nerves and in the pre-spiracular branch of the VIIth nerve. It is suggested that in its response to vagotomy the dogfish resembles a medullary mammal.
The Nerves and Muscles of Medusae
Authors: Horridge G. A.
Published: April 2021

Features of the rhythm of isolated ganglia of Aurelia are the high variability of he intervals between beats and their negative first-order serial correlation coefficient. A regular rapid rhythm or a cyclical rhythm is a consequence of stimulation. The effect of stimulation of the primary (diffuse) nerve net is usually a transient acceleration of the rhythm. A rapid, uniform rhythm is usually reset at a similar frequency by an artificially induced beat; a normal rhythm usually shows a slight pause, which is accentuated if several antidromic impulses are initiated. The pause which follows forced beats, the negative serial correlation coefficient and the time course of the return to normal after stimulation indicate a selfregulating mechanism within the ganglion. Stimulation of the ganglion with direct current can stop or accelerate the rhythm but throws no light on the possible mechanism. When the ganglion is inverted the rhythm becomes slower and more variable. Tryptamine accelerates the rhythm. The minimum effective concentration in the bathing sea water was 10-6 g./ml. Acetylcholine, adrenaline, curare, ephedrine, histamine, 5-hydroxy-tryptamine and physostigmine have no effect. The theoretical relation between the rhythm of one ganglion and of eight connected ganglia shows that the apparent redundancy of ganglia gives a more regular rhythm.
The Hydraulic Mechanism of the Spider Leg
Authors: Parry D. A. , Brown R. H. J.
Published: April 2021

The blood pressure inside the leg of the house spider Tegenaria atrica has been measured. Maintained pressures of about 5 cm. Hg and transient pressures of up to 40 cm. Hg have been found. The relation between the blood pressure in the leg and the extension torque at the hinge joints has been established. Considerable torques can be developed at the hinge joints during extension, for example, when accelerating a mass fixed to the leg. The transient pressures found to arise in the leg are adequate to account for these torques. The hydraulic mechanism is discussed. The available evidence suggests that the pressure found in the legs occurs also in the prosoma but not in the abdomen, in which case the maintained pressure must be due to the heart. This, however, requires further investigation
The Cuticular Pattern in An Insect, Rhodnius Prolixus Stål
Authors: Locke M.
Published: April 2021

The cuticle on the abdominal tergites of Rhodnius larvae has a uniform pattern of stellate pleats. In the adult this pattern is replaced by an oriented one of transverse ridges resembling greatly elongated pleats. Neither pattern results from the disposition of cells each with the potentiality for forming only part of it. The simplicity of the patterns suggests some simple mechanical cause operating over a large area. The effect upon the adult of altering the orientation and relative position of pieces of larval integument has been used to study the mechanism of orientation of the pattern. The orientation of the adult pattern is mediated through the epithelium, since rotation of the larval integument causes corresponding disturbances in the adult pattern. The epithelium has a capacity for maintaining transverse continuity within similar levels in the axis. There is an axial gradient within each segment, the anterior showing greatest facility in maintaining continuity. Pieces of transplanted integument unable to restore their continuity with the whole animal show a concentric pattern of ridges, as if the capacity for continuity had been satisfied by each level joining up with itself. Such isolated pieces of integument moult but fail to grow normally, suggesting that continuity in the axial gradient of the whole animal is necessary for the quantitative control of growth. Pieces of integument from different axial levels within a segment when juxtaposed influence the direction of displacement of the pattern according to their level. A transplant from the anterior stimulates the host ridges to maintain continuity posterior to it, and conversely.
Functional Evidence for Neurone Fields Representing the Individual Arms Within the Central Nervous System of Octopus
Authors: Wells M. J.
Published: April 2021

Octopuses blinded by section of the optic nerves were trained by means of 5-10 V. a.c. shocks to reject objects that they would otherwise take. With trials at 3, 5, or 20 min. intervals, in which the test object was always presented to the same arm, animals learned within four or five trials, thereafter rejecting the test object whenever it was presented. When, after a succession of such negative responses, the object was presented to another arm on the other side of the octopus, the result depended upon the rate of training before the change. Thus the object was taken in the trial immediately following the arm change in nineteen out of twenty-six sets of tests with trials at 3 or 5 min. intervals, but in only two out of twelve sets with trials at 20 min. intervals; further experiments in which changes were made between arms on the same side produced similar results. These results are interpreted as showing that changes occurring as a result of experience directly affecting one arm take a period of several hours to spread and become effective in determining the reactions of the rest. This in turn implies the existence of functionally independent neurone fields representing the individual arms, and is discussed in relation to what is already known about the organization of the tactile system of the octopus.
Visual Scanning in the Desert Locust Schistocerca Gregaria Forskål
Authors: Wallace G. K.
Published: April 2021

This paper describes a lateral swaying movement performed by desert locust nymphs. This movement is called ‘peering’. The angle through which the body moves is influenced by the position of objects in the visual field, showing that the movement is related to vision. When given a choice of two objects at different distances the nymphs show a preference for the nearer one. The estimation of the relative distances of the two objects is not achieved by a binocular method nor is it based on the angle subtended by the objects. An experiment is described in which an object is moved while the insect is peering. If the object is moved in the opposite direction to the insect’s motion the insect jumps short of the object. This seems to support the hypothesis that one of the functions of peering is to estimate distance by the extent of the movement over the retina of an object’s image. This method of distance estimation is discussed with relation to the binocular method. It is suggested that in some cases the peering observed may represent a preliminary scanning of the visual field and may provide information about the finer details of the field.
Pigmentation of An Ostracod,Heterocypris Incongruens
Authors: Green J.
Published: April 2021

Heterocypris incongruens contains at least three different types of pigment: carotenoids, a pteridine, and a bilin. Haemoglobin and other haem pigments appear to be lacking in this species. Astaxanthin and β-carotene are the only carotenoids found, even when the ostracod is feeding on algae containing abundant xanthophylls of various types. A yellow pteridine, which rapidly decolorizes after extraction, is widespread in the body of the ostracod, but not in its eggs. It is suggested that this substance may play a part in the intermediate metabolism of the ostracod when in anaerobic conditions. Heterocypris can live and reproduce in anaerobic conditions for at least 2 weeks. Biladiene pigments accumulate in the gut wall when the ostracod feeds on blue-green algae. These pigments can be made to disappear from the gut wall by restricting the diet to green algae, then made to reappear when a blue-green alga is given as food.
The Role of the Epidermal Cells in the ‘Migration’ of Tracheoles in Rhodnius Prolixus (Hemiptera)
Authors: Wigglesworth V. B.
Published: April 2021

During the moulting process the tracheal system grows by the extension of new tracheae and tracheoles from the existing tubes. Outgrowths are produced by the active movements of the formative cells of the tracheal epithelium; these give out filiform ‘amoeboid’ processes which move into those regions most deficient in oxygen (Wigglesworth, 1954).
The Jumping Mechanism of Salticid Spiders
Authors: Parry D. A. , Brown R. H. J.
Published: April 2021

Photographs of the jumping spider Sitticus pubescens (Salticidae) show that the jump is almost entirely due to the sudden straightening of the fourth pair of legs. Multiple-image photographs show the importance of a silk drag-line in controlling the jump. The torques at the leg joints have been estimated. Extension torques occur at the two hinge joints although these lack extensor muscles. The erection of leg spines at the moment of the jump provides direct evidence that hydraulic forces are involved in the jump. This view is supported by estimates of the pressures involved, which fall within a factor of about two of those previously measured in the legs of the spider Tegenaria.
Studies on the Metabolism of Locust Fat Body
Authors: Clements A. N.
Published: April 2021

The successive accumulation and depletion of reserves in the fat body of insects shows that it is an important storage organ, but it seems possible that it is also an organ of intermediary metabolism, degrading some substances and elaborating others for use by other tissues. A study was made in vitro of the incorporation of certain metabolites, glycine, leucine, acetate and glucose, labelled with carbon-14, into the fat body of the desert locust, Schistocerca gregaria Forskal. This showed something of the degradation and synthesis occurring in locust fat body and also suggested that the tricarboxylic acid cycle functioned normally, contrary to an earlier report (Hearfield & Kilby, 1958). The results obtained from these studies on the incorporation of labelled metabolites and on the respiration of locust fat body are presented here.
The Mechanism of Gill Ventilation in the Dogfish and Skate
Authors: Hughes G. M.
Published: April 2021

The respiratory movements of the dogfish, ScyUorhinus (Scyllium) canicula (L.), and the ’skate’, Raia clavata L. (thornback ray), have been studied by the use of cinematographic and mechanotransducer recording methods. Simultaneous determinations of the time-course of pressure changes in the oro-branchial and parabranchial cavities were also made by means of Hansen condenser manometers. In both species movements of the mouth precede those of the spiracular valve and of the branchial region. Adduction and abduction of the branchial region spreads serially from the first to last gill slit in the dogfish, but movements of the individual gill arches are more nearly synchronous in the skate. Opening of the flap valves formed by extensions of the inter-branchial septa are synchronous in both species. Water entering one side of the mouth leaves by the three posterior gill slits of the same side. Water entering the spiracle leaves through the anterior slits of the same side. This separation of flow is less marked in the skate. The pressure curves recorded in all parts of the system have both positive and negative phases with respect to the external medium. The positive phase, associated with closing of the mouth and spiracle, is larger in the oro-branchial than in the parabranchial cavities and vice versa. The time-course of the pressure changes indicates that the flow across the gills is maintained by the action of a pressure pump in front and a suction pump behind. The suction pump plays a more important role than the pressure pump in the skate and its contribution to the flow across the gills is by no means negligible in the dogfish. The differential pressure curves suggest that the flow across the gills is continuous except in the dogfish for a brief period when the gradient is reversed. The absence of this reversal in the skate suggests that the external gill slit openings are controlled by an active mechanism. This is probably an adaptation to bottom-living habit. All these observations relate to animals which are stationary with respect to the water. During swimming at a reasonable speed leopard sharks (Triakis semifasciata) have been observed to make few or no respiratory movements, although they immediately ventilate actively on coming to rest at the bottom of the aquarium.
Sodium Regulation in the Crayfish Astacus Fluviatilis
Authors: Bryan G. W.
Published: April 2021

In external sodium concentrations of up to 100 mM./l. the blood sodium concentration of Astacus is only slightly increased. As the external level approaches or exceeds the normal blood sodium concentration of 200 mM./l. so the increase becomes more marked. Similarly, there is an increase in urine sodium concentration. This net gain of sodium is accompanied by a considerable rise in sodium outflux as shown by 22Na. At external concentrations exceeding 300 mM./l., blood and urine concentrations rise to a similar level and active sodium movements appear to cease. With increased blood sodium concentration the level in the muscles rises also. This relationship is not one of simple proportion and at high concentrations there is relatively more sodium in the muscles. In artificial tap water animals with a high blood concentration lose sodium until the normal level is regained. This net loss is due to influx being much lower and outflux much higher than normal. Of the outflux, up to 70% is initially due to renal losses and losses over the body surface are higher than normal due to the excess sodium in the blood. From the results given in this and previous papers the way in which sodium balance may be achieved under normal conditions is discussed.
The Effect of Perturbations in the Environmental Cycle of the Diurnal Rhythm of Activity of Periplaneta Americana L
Authors: Harker Janet E.
Published: April 2021

The locomotor activity rhythm of Periplaneta americana in alternating light and darkness is described as consisting of six stages. The effect on the suboesophageal ganglion neurosecretory cycle of a change from light to darkness at each stage of the locomotor rhythm is described, and three stages in the neurosecretory cycle are recognized. The effect on an established locomotor activity rhythm of a change to darkness at various times of day is described in terms of the immediate reaction of the animal and of the subsequent phase relations of the rhythm. The phases of the activity rhythm are not reset if the environmental change occurs during the active period. The final positioning of the phases, when the onset of darkness occurs during the non-secretory phase of the neurosecretory cycle, is dependent upon the subsequent light conditions; transient activity peaks may appear before the stable position is reached. The dependence of the neurosecretory cells on some other centre for the provision of some secretory substance, or precursor, is discussed.
Heat Loss and the Body Temperatures of Flying Insects
Authors: Church Norman Stanley
Published: April 2021

Comparative measurements of body temperatures and water loss in Schisto-cerca gregaria showed that evaporation dissipates relatively little of the heat generated by the wing muscles during flight. In perfectly dry air at 30°C., evaporation reduces the temperature excess of the pterothorax by less than 10%, or about 0·5°C. Even at 40°C., which is the highest temperature that will permit continuing flight, the reduction is only about 20%, or 1·2°C., in dry air. A flying locust has no special mechanism, except cessation of flight, to protect it from overheating. Breathing is not markedly increased at high temperatures, nor is the rate of heat production reduced. Very little heat is dissipated from the pterothorax by evaporation through the cuticle. The cuticle becomes permeable enough to allow substantial cooling only at temperatures well above the highest that permit flight. Temperature measurements in Triphaena pronuba and Bombus lapidarius supported the idea that evaporative cooling during flight is not much more important in other well-waterproofed insects. Large changes in the humidity produced changes of less than 1°C. in the temperature excess, even at the highest air temperatures at which the insects could fly. The reactions of the insects to moist and dry air are adapted to the conservation of their water rather than to rapid cooling.
Heat Loss and the Body Temperatures of Flying Insects
Authors: Church Norman Stanley
Published: April 2021

The natural internal temperature gradients during flight were reproduced in various medium and large insects by mounting freshly killed specimens in a wind tunnel and heating them with a high-frequency electric current. The heat flow from the flight muscles to other parts of the body and from the body were investigated. Comparison of dead and living insects showed that most of the heat transfer within the body is by conduction; circulation of the haemolymph during flight contributes little to the heat flow. The temperature excess is high throughout the pterothorax in a large insect; where there are no subcutaneous air sacs it is only about 10% less at the surface of the pterothorax than at the centre. Only about 5-15% of the heat generated in the flight muscles is conducted to the prothorax, head, abdomen and appendages, which remain near the temperature of the air. Usually not more than 10-15% of the heat escapes from the pterothorax by long-wave radiation in a large insect flying under a clear sky. Smaller insects lose relatively more of their heat by radiation. Radiation increases with the insect’s temperature but it is never sufficient to give much protection against overheating. Ordinarily 60-80% of the heat is dissipated from the surface of the pterothorax by convection. In convection from a naked insect the relationships between heat loss, the surface temperature excess, size, and wind speed are nearly the same as in convection from a smooth cylinder or sphere, if allowance is made for turbulence in the air flow over the insect. In dragonflies and denuded bees and moths heated in proportion to their pterothoracic volumes in a constant wind, the temperature excess was proportional to the 1·3-1·5 power of the average diameter of the pterothorax. The coats of hair on bumble-bees, hawk moths, and noctuid moths are excellent insulators against convective heat loss. At normal flying speeds they increase the temperature excess by 50-100% or more--in a large hawk moth probably by at least 8 or 9° C. The insulating value of a coat depends mostly on its density and on the size of the insect, and less on the length of the hair. In dragonflies the pterothorax is insulated nearly as effectively by the subcutaneous air sacs.
Nervous Control of Movement in Annelids
Authors: Wilson Donald Melvin
Published: April 2021

Nerve muscle preparations of the segmental nerves and associated muscles have been made using a nereid polychaete, Neanthes brandti (Malmgren). Two kinds of response, differing in threshold and latency, were found. The ‘fast’ response is large at the first shock and (at frequencies above 1/sec.) decreases thereafter. The ‘slow’ response is small but facilitates with repetition at frequencies above 10/sec. Facilitation reaches a maximum after 3 or 4 shocks. Isolated parapodia show several distinct reflex movements to mechanical and chemical stimuli. These must involve motor neurons in the parapodial ganglion. Stimulation of the segmental nerves of the leech, Hirudo, evokes facilitating muscle potentials resembling in most details those of the ‘slow’system in Neanthes. The ‘fast’ and ‘slow’ responses are discussed in comparison with other invertebrate systems, especially those of arthropods. The ‘slow’ responses in annelids show less facilitation. The ‘fast’ responses of polychaetes fatigue quickly and are probably useful only in ‘startle’ responses.
Nervous Control of Movement in Cephalopods
Authors: Wilson Donald Melvin
Published: April 2021

Nerve muscle preparations have been made of the mantle and stellar nerves of octopuses and squids. Two motor innervation systems have been found in each. Both have been observed as unit preparations. The possibility of double innervation of the same muscle cells exists but has not been directly checked. The fast innervations produce electrical responses which are maximal to the first stimulus and which have little or no absolute refractory period. They appear to be local rather than spike potentials. Fatigue is very rapid. The mechanical response sums in Octopus, but not in Loligo. The slow innervations produce electrical and mechanical responses which facilitate with repetition. The fast system of Loligo does likewise after fatigue to a low level of response. No evidence was found for a functional nerve net in the mantle. Organizational features of the stellate ganglion have been identified physiologically in Octopus. The ganglion acts both as an integrating motor centre and as a reflex centre.
Neural Mechanism of Hearing in Insects
Authors: Katsuki Yasuji , Suga Nobuo
Published: April 2021

The frequency response ranges of the tympanal and cereal nerve were measured in ten species belonging to four families, Cicadidae, Acridiidae, Tettigoniidae and Gryllidae. The tympanal organs of Acridiidae and Tettigoniidae responded to ultrasonic waves and the most effective frequency was very high (> 10 kc./s.), while the response ranges of the other two families, Cicadidae and Gryllidae, were within that of man. The response ranges of the cereal nerves (lower) and tympanal nerves (higher) were partly overlapping. Stridulation consisted of pulsatory sounds and had species-specific rhythms, to which the tympanal nerves responded with synchronous discharge. The dominant frequency range involved in stridulation agreed well with the frequency range to which the tympanal organ of the same insect was most sensitive. The threshold of the tympanal nerve varied with different directions of incident sound, especially for ultrasonic waves, indicating the possibility of directional sense. Tympanal neurons of Gampsocleis buergeri were referable to two types having different response ranges. The curves relating number of spikes per second to intensity of stimulus were sigmoid and almost parallel for different frequencies. In Discussion it is pointed out that although no single receptor organ is able to discriminate stimulus frequency, an insect which has different sound receptors on various parts of its body may have some power of discrimination.
Neuronal Pathways and Synaptic Connexions in the Abdominal Cord of the Crayfish*
Authors: Hughes G. M. , Wiersma C. A. G.
Published: April 2021

As material for the study of functional connexions within a central nervous system, invertebrates with ganglionated nerve cords appear to offer advantages absent elsewhere. In such animals it should be possible to lead off from the axons which transmit the information from one synaptic region to another at all levels in the connectives, provided there are no cells or synapses in these connectives. In the crayfish, it has been previously shown that such an analysis is indeed possible, at the level between the ‘brain ‘and the remainder of the ventral cord. It was found (Wiersma, Ripley & Christensen, 1955) that many interneurones respond to stimulation of several segments of the body, usually to stimulation of homologous areas of the individual segments. Three fundamentally different ways in which the inflow to different ganglia may become integrated in this way were suggested by Wiersma (1958), and are illustrated diagrammatically in Fig. 1. To gain further information about the occurrence of these different types, it was desirable to obtain recordings from interneurones at a lower level in the cord where the actual integration takes place. The isolated abdomen preparation proved highly suitable for this purpose. The number of fibres in each connective here is still smaller than that in each circumoesophageal commissure (about 1200 as against about 2000), and it was found possible to obtain from the cord preparations in which unit responses were clearly recognizable with not much more difficulty than from the commissure. Altogether it was possible to account for some 75 definite entities as against 100 in the commissure. In both places some of these are not single fibres but bundles of primary sensory fibres with similar properties. In the cord such bundles are more frequent than in the commissure. The nature and distribution of these entities will be described elsewhere; in the present paper their physiological properties will be discussed with special reference to the evidence they provide for the existence of these three possible types of integration. The results will show that the one in which a single interneurone collects impulses from different ganglia (scheme C of Fig. 1) is certainly realized in many of these interneurones.
The Thickness of Some Insect Epicuticular Wax Layers
Authors: Lockey Kenneth H.
Published: April 2021

The average thickness of the epicuticular wax layers on the wing membranes and elytra of a number of different insects has been measured by relating the volume of extracted wax to the area of cuticle over which it was spread. The true surface area of the epicuticle was measured by krypton adsorption. The ratio of absorption area to apparent projected area was found to be 1·6 for the wing membranes, and 6·7–8·2 for the elytra, with an average value of 4·1. The wax layers were found to be remarkably similar in thickness on the wing membranes, ranging from 0·11 to 0·13 μ but to vary from 0·11 to 1 ·26 μ in the case of elytra, where the wax thickness appears to be related to extent of modification.
The Development of Salinity Tolerance in the Salmon, Salmo Salar (L.) and Some Related Species
Authors: Parry Gwyneth
Published: April 2021

A study has been made of the survival and osmotic regulation of young salmonid fishes following transfer from fresh water to various dilutions of sea water Survival is in the order: and is generally better the larger the fish. The survival pattern of alevins differs from that of the older stages. Hypo-osmotic regulation is first seen in parr and becomes fully effective in smolts.
The Determination of Total Carbon Dioxide in Water
Authors: Milburn T. R. , Beadle L. C.
Published: April 2021

The method described involves extraction of the dissolved gas from an acidified sample in a modified van Slyke apparatus, and measurement of the electrical. resistance of a standard sodium hydroxide solution before and after equilibration with the extracted gas. The original sample must be not less than about 30 ml. for which a 10 ml., sample is drawn into the extraction apparatus. There is a linear relation between the resistance finally measured and the total carbon dioxide content of the original sample up to a maximum determined by the strength of the standard hydroxide solution, which is thus adjusted to the desired range of carbon dioxide concentration, e.g. 0 ·005 N-NaOH for 0 –50 mg./L and 0 ·02 N for 0 –200 mg./l. CO2. The method is easily sensitive to 0 ·3 mg./l. in the range 0 –50 mg./l. total carbon dioxide and about 1 mg./l. in the range 0 –200 mg./l. With a rigidly standardized procedure increased accuracy was obtained so that replicate determinations, on standard solutions in the 0 –50 mg./l. range did not differ by more than 0 ·16 mg./l. Precautions for handling samples containing carbon dioxide in solution prior to determination have been suggested. About 15 –20 min. are required for each determination and to Mrs D. E..
A Cineradiographic Study of Respiration inMyxine GlutinosaL
Authors: Johansen Kjell , Hol Ragnar
Published: April 2021

The anatomy of the respiratory organs, as well as the mechanism of breathing in myxinoids, is distinctly different from that in all other fish-type craniotes even including the petromyzonts. In Myxine the branchial gill lamellae are enclosed in rounded sac-like pouches, with ducts conveying the water from the oesophagus to the gills from which it travels through efferent ducts uniting on each side, finally leaving the animal through paired branchial apertures. In addition to the paired gill pouches there exists an oesophago-cutaneous duct connecting the pharynx to the exterior behind the left, last gill sac. The exterior opening is confluent with the left gill pore. Regarding the course of the respiratory current in this system contradictory explanations have been presented. More recent authors seem, however, to agree upon the concept that the water current is solely dependent upon the pulsating activity of the velum and is not influenced actively by either the gill pouches or their ducts (Gustafson, 1935; Strahan, 1958; Marinelli, 1956). The velum and its connected muscles, which is a unique structure in myxinoids, was already anatomically described by Müller in his Myxine monograph (1835) and later by Fürbringer (1875) and Cole (1907). The first two authors, however, did not contemplate the velum as being of any functional value for respiration. Cole, on the other hand, suggested a role for this structure in the maintenance of the respiratory current. Goodrich (1930) has advocated that breathing in Myxine takes place by expansion and contraction of the muscular elements in the gill sacs. That the gill sacs in Myxine contain distinctly striated muscular elements has been described by Cole (1912) and later by Goodrich (1930) and Hofbauer (1937). It seems obvious, upon reviewing the literature, that the physiological interpretations of this problem in earlier works are mostly founded on anatomical studies with little or no physiological experimentation. The excellent works of Gustafson (1935) and Strahan (1958) base their functional interpretations entirely upon external observations of the living animal or upon dropping coloured solution in the respiratory water and following its course into the nostril and out of the branchial apertures. The present study attempts to analyse the mechanics of respiration in Myxine by utilizing modern cineradiographic equipment which allows fluoroscopic examination of all events inside the respiratory passages; these may be recorded on a camera at 26 frames per second. The method has been used earlier for the study of the circulation in snakes (Johansen & Hol, 1960) and of the central circulation in Myxine (Hol & Johansen, 1960).
Proprioception and Visual Discrimination of Orientation in Octopus
Authors: Wells M. J.
Published: April 2021

Twenty-two small octopuses were trained to make visual discriminations before and after removal of the statocysts. Removal of one statocyst (left or right) did not affect performance in a visual discrimination of rectangles shown horizontally and vertically (8 experiments), nor did it determine which eye was used to guide attacks upon things seen (a record of this was kept in four of the experiments). Removal of both statocysts did not affect performance in a discrimination between black and white circles (7 animals) but did destroy the capacity to discriminate successfully between rectangles shown horizontally and vertically (11 animals). After removal of both statocysts the orientation of the retina (as indicated by the slit-like pupils) is no longer constant over the normal wide range of bodily positions, but depends upon how the animal is sitting on the side or bottom of its tank. An analysis of the postoperational responses of animals trained to make the orientation discrimination showed that nearly all of them were biased in favour of one or other of the test figures, not always that used as ‘positive’ figure during preoperational training. The postoperational scores of these trained animals depended mainly upon the positions in which they habitually sat in their tanks; ndividuals in positions such that the retina of the eye used to observe the test figures lay at right angles to the position held during pretraining tended to behave perversely. These results indicate that orientation discrimination is dependent upon correct orientation of the retina, rather than upon central integration of proprioceptive and visual information. This is discussed in relation to a possible mechanism of visual discrimination proposed by Sutherland (1957), and in relation to what is already known about the role of proprioceptive information in learning.
The Nutrition of the Central Nervous System in the Cockroach Periplaneta Americana L
Authors: Wigglesworth V. B.
Published: April 2021

The organs and tissues of insects are mostly composed of single layers of cells separated from the circulating blood by thin connective tissue membranes (Wigglesworth, 1956a; Pipa & Cook, 1958). The supply of nutrients to such organs presents no problem. But the central nervous system is an exception. The ganglia are the only solid organs in the insect body. They consist of densely packed peripheral cells surrounding a central neuropile, the whole ganglion being covered by a tough fibrous sheath or neural lamella continuous with the connective tissue membranes elsewhere. The total thickness of the ganglion may be 1 mm. or more.
The Physical Basis of Astro-Navigation in Birds: Theoretical Considerations
Authors: Pennycuick C. J.
Published: April 2021

Matthews’s hypothesis of sun navigation in its original form is rejected on the grounds of physical impossibility of making one of the measurements, and an invalid assumption in the reasoning. It is suggested that the bird should measure the sun’s altitude and rate of change of altitude. The position lines corresponding to these quantities are discussed, and the way in which birds might make and use such observations is considered. The sensory performance required is shown to be reasonable. The magnitude and direction of the errors of position resulting from various sorts of errors of observation are discussed in relation to the experimental evidence. Suggestions are put forward for future experiments.
Studies on the Exchange and Regulation of Sodium in the Larva of Aedes Aegypti (L.)
Authors: Stobbart R. H.
Published: April 2021

The net transport of sodium into the haemolymph by sodium-deficient 4th-instar larvae of Aëdes aegypti (L.) has been studied by means of flame photometry. The fluxes associated with this net transport have been studied by means of 22Na. The net transport is much more rapid in fed larvae (rate about 50 mM./l./hr.) than in starved larvae (rate about 10 mM./l./hr.). The fluxes are also much greater in the fed larvae. The fluxes associated with net transport in fed and starved larvae are much greater (initially at any rate) than the fluxes occurring in normal fed and starved larvae during steady-state exchange. In both fed and starved larvae almost all the net transport and the fluxes associated with it occur through the anal papillae, so these organs must be responsible for almost all the difference between fed and starved larvae in the rate of net transport and fluxes. Cytological changes in the anal papillae following upon feeding and starvation are described. The results are discussed in terms of possible carrier mechanisms in the anal papillae.
Aspects of Flight Mechanics in Anisopterous Dragonflies
Authors: Neville A. C.
Published: April 2021

Movements of the wings and pterothorax of Aeshna spp. have been studied by stroboscopic observation combined with the cutting of certain muscles. There is a constant phase difference between the contractions of the mesothoracic and metathoracic flight muscles, and a resulting phase difference between the movements of the wing-base sclerites and wings in the two pterothoracic segments. As the wings in each segment move upwards and backwards, the respective notal sclerites are moving forwards and downwards. Conversely, as the wings beat forwards and downwards, the nota move backwards and upwards. The anterior coxoalar elevator muscle pulls on the anterior lobe of the lateroprescutum and so, via the membrane on the posterior edge of the humeral complex. This causes extensive supination of the wing, important in hovering and backward flight, and is due to a sudden snap-like separation of the humeral and axillary complexes about a fine of weakness between them when the descending wing is at io° from its lowest position. Both remotion at the end of the downstroke, and the complex propeller-like supinated wing section which develops during the last 10° of the downstroke and most of the upstroke, are made possible by the line of weakness running along the membrane between the two complexes. Comparison of manipulated wingstrokes with normal wingstrokes showed that supination is actively controlled in the flying insect by muscular contraction. Scutal ascension, described in the paper, was detected. At any point on the downstroke, the scuta occupy higher and more posterior positions than they do at the corresponding point on the upstroke. Fore and aft movements of the nota are greater during flapping flight at low wingbeat frequency, than during full flight at higher wingbeat frequency. The prescutum, scutum and scutellum move together as a unit up and down and fore and aft, throughout the wingstroke cycle. Supination during the last 10° of the downstroke and the first half of the upstroke is due to the anterior coxoalar muscle, and during the second half of the upstroke to the third subalar muscle. Downstroke pronation/supination balance is controlled by the basalars and second subalar. A detailed summary of these rotation balances is given in the discussion. The oblique intersegmental muscle of the metathorax is shown to be an abdomen elevator and not a wing depressor. The functions of the various flight muscles are demonstrated experimentally for the first time. The anterior coxoalar muscle is shown to be specialized, functioning in elevation and supination and assisting remotion.
The Effects of Ions and Drugs on Neuromuscular Preparations of Sea Anemones
Authors: Ross D. M.
Published: April 2021

Isolated preparations of the columns of Calliactis and Metridium take up a basic extended length and show repeated contractions at intervals of a few minutes to half an hour. The preparations respond to stimuli with slow movements whose latencies range from about 20 sec. to 2 min. Direct contractions and higher tonus of the preparations are caused by excess K.+ and by Mg2+-free sea water; excess-Ca2+ raises tone slightly. Activity is greatly enhanced by Mg2+-free water, and moderately enhanced by excess K+ and excess Ca2+. It is abolished by excess Mg2+ and Ca2+-free sea water, but not by sea water free of both Ca2+ and Mg2+. In K+-free sea water and in Na+-free sea water activity declines slowly and responses to stimuli still occur for at least 1 hr. Except for some enhancement by excess Ca2+ and the depression with excess Mg2+ and Ca2+-free sea water, responses to stimuli are not much affected by ions. Acetylcholine and associated drugs, and also histamine, 5-hydroxytryptamine, and many other substances, have no significant effects on the tone, activity, or responses of column preparations. Adrenaline raises tonus at a concentration of 1 × 10-6; at 1 × 10-5 and above; it causes direct contractions, enhanced activity and high tonus, but it has no effect on responses to stimuli. Noradrenaline, dopamine, tyramine, and other related compounds, as well as various adrenergic blocking agents, are totally inactive. Tryptamine, at concentrations of 1 × 10-4, causes direct contractions, high tonus and enhanced responses to stimulation. 5-Methoxytryptamine has similar effects. To be effective, treatments must be applied directly to the contractile part of the preparation. Applying the active ions and drugs to attached strips of column has no effect. Some comparative and functional aspects of the results are discussed.