bluuebunny/crossref_metadata_2025 huggingface dataset:
Facilitation in Sea Anemones
Authors: Ross D. M.
Published: April 2021

The previously reported effect of anemone extracts, the occurrence of quick closing responses to single electrical stimuli in Metridium, has been re-investigated. In standardized tests it was found that whereas hundreds of stimuli are required for each response to a single stimulus in untreated animals, after anemone extract the incidence of such responses is one per nine stimuli. The incidence of these responses falls off with decreasing doses of extract and the effect disappears when less than of the material from a single large Metridium is administered. There is no evidence that extracts from ‘stimulated’ and ‘unstimulated’ (i.e. anaesthetized or quick-frozen) anemones differ in potency. Extracts from divided animals show greater activity in the ‘sphincter-disk’ fraction. The incidence of the responses also falls off in time and is highest from 15 to 30 sec. after beginning the treatment. The effect is sporadic and short-lived and responses to two or more successive stimuli are exceptional. A number of treatments, such as drastic changes in pH, KC1(K+ × 8), tetramethylammonium hydroxide (1 : 100), NH4C1 (1 : 340) and especially bile salt and saponin, have similar effects. Drugs with neuro-muscular effects elsewhere (acetylcholine, adrenaline, tyramine, histamine, etc.) were generally ineffective except at very high doses. Food stimulants too were ineffective. From the time relations and other aspects of the responses to single stimuli it is concluded that the effect should not be attributed to a substance with the function of a ‘facilitator’ in the living animal. While the effects are consistent with the passage of occasional adventitious impulses in the nerve net, there is a singular absence of spontaneous or post-stimulus contractions. Certain implications of this feature of the results are discussed.
The Freezing, Drying and Storage of Mammalian Skin
Authors: Billingham R. E. , Medawar P. B.
Published: April 2021

The viability and general preservation of skin that has been subjected in vitro to freezing, drying and other procedures may be tested by transplanting it back to the animal from which it was originally removed. Rabbit’s ear skin withstands either slow or rapid freezing down to the temperature of liquid air. Slow freezing gives better preservation than rapid freezing, but impregnation with glycerol solutions protects skin against some of the harmful consequences of rapid freezing. Epidermal melanoblasts do not withstand rapid freezing unless they have been protected by glycerol solutions. Rapid thawing gives better preservation than slow thawing. Malpighian cells of the epidermis survive slow thawing after impregnation with glycerol solutions but not after impregnation with Ringer’s solution. Skin slowly frozen after impregnation with glycerol solution and stored for 4 months at—79°C. was indistinguishable, on transplantation, from a freshly removed graft. The storage of skin at—79°C. does not result in progressive deterioration during the period of storage. It is shown that the toxicity of glycerol to the various cellular constituents of skin is so slight that it may be disregarded. Isolated epidermal cells withstand exposure to 98·1 % glycerol at room temperature for half an hour. Skin does not withstand dehydration to a degree that results in a final overall water content below about 25 %. Impregnation with glycerol solutions does not increase its capacity to withstand dehydration.
Preliminary Observations on the Mechanism of Cleavage in the Amphibian Egg
Authors: Waddington C. H.
Published: April 2021

The formation of blastomeres by the newly fertilized egg has been studied by many authors, who have found the process a convenient avenue for attacking the general problem of cell division. By far the greater part of the work has been carried out on the eggs of marine invertebrates, and, in spite of their great suitability for most types of experimental embryological investigation, the eggs of Amphibia have not as yet been made much use of in this connexion. The nuclear phenomena attendant on fertilization and cleavage in the Amphibia have been rather fully described (see, for instance, Fankhauser & Moore, 1941), but a short note by Schechtman (1937) contains almost everything that we know about the cleavage of the cytoplasm, and the part played in it by cortical movements.

During the last two summers a few experiments have been made which show that the amphibian egg provides very favourable material for a direct attack on certain of the crucial problems of cell division, since not only is it rather easy to perform micro-surgical operations on the developing cleavage furrow in a manner which would be very difficult in the small eggs of most invertebrates, but the pigmentation of the surface allows the cortical movements to be followed precisely in time-lapse cinema films. These experimental opportunities have not yet been by any means fully exploited, but the preliminary experiments have already yielded certain results which it seems worth while to record.

The experiments were made with eggs of Triturus alpestris which were laid and fertilized normally in the aquarium. The eggs were observed in Holtfreter solution, either of normal strength, or diluted with an equal volume of distilled water.
The Preferences of Honeybees for Solutions of Various Sugars Which Occur in Nectar
Authors: Wykes G. R.
Published: April 2021

In field and in laboratory experiments bees were offered equal volumes of sugar solutions, of different composition but the same total concentration. It was found that sugars which occur in nectar were not equally attractive to bees. Consistent preferences were shown for solutions of single sugars in the following descending order : sucrose, glucose, maltose, fructose. The acceptances of some mixtures differed from those predicted on the basis of an additive effect of the constituent sugars. Anomalous high preferences were shown for sucrose-glucose-fructose solutions. The concentration of the solution appeared to influence the observed preferences, the relative acceptances of solutions at normal threshold level differing from those at higher levels in the series of laboratory experiments. No direct relationship appeared to exist between the chemical constitution of the sugars offered and their acceptance by bees; and no evidence was found to explain the observed differences in preferences for solutions of either single or mixed sugars. Attention is drawn to the possible biological significance of such selective responses by bees—it appears that the sugar composition of nectar may be a contributory factor influencing the visits of bees to flowers.
Diapause in Lucilia Sericata (MG.) Diptera
Authors: Cragg J. B. , Cole Patricia
Published: April 2021

Data collected over a period of 2 years have shown that diapause in 3rd-instar larvae of Lucilia sericata (Mg.) may be of maternal origin and that its incidence gradually increased in the latter part of the blowfly season. The age of female flies has no significant effect on the amount of diapause. The capacity to give diapausing batches was lost by the majority of flies kept under standard laboratory conditions for 10-16 days.
The Size of Ommatidia in Apposition Eyes
Authors: Barlow H. B.
Published: April 2021

In a compound apposition eye the acuity may be limited by the interommatidial angle or by the optical performance of each ommatidium. In the honeybee the performance of the ommatidia must approach the theoretical limit set by diffraction if the whole eye resolves points separated by twice the inter-ommatidial angle. The eyes of twenty-seven other species of Hymenoptera were measured, and the results show that in eyes of different sizes the number of ommatidia is adjusted so that inter-ommatidial angle is just below the limiting resolving power of the ommatidia; this is the condition for optimum acuity in a compound apposition eye. When this condition is fulfilled the minimum resolvable angle is inversely proportional to the square root of the linear dimensions of the eye. Acuity increases with size more rapidly in the simple type of eye.
Studies on Insect Metamorphosis
Authors: Singh-Pruthi Hem
Published: April 2021

Kellog and Bell (1904) working on the silkworms noticed that if they were fed on insufficient quantities of leaves, their larval life was prolonged, i.e., their pupation or metamorphosis was postponed. Northrop (1917) showed the same state of things in the flies, Drosophila, when reared on food containing little or no yeast. Then, Tangl (1909 (a) and (b)) observed that if the flies were bred on unsuitable food which they did not readily take, they pupated a week later than the normally fed individuals. Thus the researches of all these authors indicated that inadequate feeding, qualitatively or quantitatively, delays metamorphosis. But this general conclusion was contradicted by the works of Krizenecky (1914) and of Szwajsowa (1916) on mealworms (Tenebrio molitor) which pupated much earlier when starved. In order to determine how far the above mentioned general conclusion could be modified, several experiments have been performed on mealworms, of different stages of growth, the results of which are reported in the following pages.
The Structure of Chromosomes
Authors: Belling John
Published: April 2021

When pollen-mother-cells (or young microspores) of a plant with large chromosomes are mounted in iron-acetocarmine (1), torn chromosomes usually appear to have the consistency of honey or glue, long curling threads extending out from the broken ends. The cytoplasm is more liquid (stage 1). In a day or two, however, the cytoplasm has usually attained the consistency of a firm jelly or of cheese, while the chromosomes are still harder (stage 2). In this state the cell contents may be squeezed flat by carefully graduated pressure, without injury to the chromosomes. In the course of time the hardening progresses, until both cytoplasm and chromosomes become more or less brittle under pressure (stage 3).
Counting Live and Dead Bull Spermatozoa
Authors: Campbell R. C. , Hancock J. L. , Rothschild Lord
Published: April 2021

An investigation has been made into the accuracy of estimates of the proportions of dead spermatozoa in diluted and undiluted bull semen, using the nigrosineosin live-dead staining technique. Two operators counted 24,673 spermatozoa, in lots of approximately 200, on smears derived from a number of subsamples taken from the same ejaculate. The variations between different counts made on one smear were consistent with random sampling from a binomial population; the same applied to variations between slides made from one subsample; the variation between subsamples were, however, larger than would have been expected on the basis of random sampling. Undiluted semen and semen diluted 1/4 with Ringer-phosphate-fructose solution had the same mean percentage dead and precision of estimation. Tables are given showing how the precision of an estimate of the proportion of dead spermatozoa in a sample varies according to the percentage of dead spermatozoa, the total number of spermatozoa counted and according to the number of subsamples taken from the original ejaculate, each subsample being used for making counts.
Exchanges of Sodium and Potassium in Mosquito Larvae
Authors: Ramsay J. A.
Published: April 2021

The movements of sodium and potassium through the body and their exchanges between the body and the external medium have been studied in the larva of Aedes aegypti L. Briefly, both elements enter the body via the anal gills, are excreted by the Malpighian tubules and can be absorbed from the tubule fluid in the rectum. When either element is present in the medium to excess its concentration in the tubule fluid is increased and the extent of its absorption in the rectum is decreased. Under all conditions the concentration of potassium in the tubule fluid is greater than its concentration in the haemolymph, and the concentration of sodium is less. There is a circulation of potassium from haemolymph to tubule, to rectum or midgut and so back to haemolymph. The composition of the haemolymph in respect of sodium and potassium is remarkably constant in the face of changes in the medium. The volume of the larva appears to be regulated by a nervous mechanism. If the volume is increased peristaltic waves pass down the intestine more frequently and more fluid is voided through the anus.
A New Method of Measuring the Activity of Spermatozoa
Authors: Rothschild Lord
Published: April 2021

A new and quantitative method of estimating the average speed of a suspension of spermatozoa has been developed. The method, in which the phenomenon known as probability-after-effect and kinetic theory principles are made use of, can be applied to any system of organisms which move in random directions, in one, two or three dimensions. The experimental procedure is to place a drop of sperm suspension on a microscope slide with a cover-slip on top of the drop, and photograph the spermatozoa at known time intervals. The number of spermatozoa in a region of known size is counted on each photograph. The estimated mean or average speed of the sperm suspension, , is given by the equation where r is the radius of a circular region in which the number of spermatozoa is counted, τ is the time interval between photographs, is the average of the square of the differences between the numbers of spermatozoa counted on consecutive photographs, and is the average number of spermatozoa in the circular region. Appropriate formulae for non-circular regions and for the precision of estimates of are given. A method of testing whether the directions of movement of spermatozoa are random has been applied to bull semen diluted 1/4 with phosphate buffer containing fructose. The movements were found to be random. The distribution of sperm speeds was determined and found to be somewhat skew and leptokurtic, with mean 123 µ/sec. and standard deviation 39. If dead or motionless spermatozoa were included, the mean speed became 117 µ/sec. Using the probability-after-effect equation given in (3), the mean speed of the suspension, including dead or motionless spermatozoa, was found to be in 111 µ/sec., with a standard error of 24·5. The standard error and therefore the precision of the estimate is under the control of the experimenter. Practical instructions for carrying out measurements are summarized in a separate section.
Observations on Certain Mechanical Properties of the Ligament of Pecten
Authors: Trueman E. R.
Published: April 2021

The ligament of Pecten maximus consists of two layers, the outer extending along the dorsal margin of the valves, and the inner situated between the valves in the region of the umbo. The former appears fibrous and is somewhat similar to the outer layer of other ligaments. The inner layer consists of three parts, a large central noncalcified structure and two lateral calcified regions attaching the former to the valves. The central region is characteristic of the ligament of P. maximus and associated species, this layer being uniformly calcified in the ligament of most bivalves.

When the valves are closed the outer layer is subjected to tensile stress and the inner to compression, and the force so derived tends to open the valves. This force and that required just to close the shell are expressed as the opening and closing moments of the ligament respectively, and these have been determined for various lamellibranchs.

The exact conditions of the opening and closing of the valves have been observed by drawing the stress-strain curves for the intact ligament, plotting the applied moment against the angle of gape. The loading and unloading curves so produced describe a hysteresis loop. The area enclosed in that of Pecten (or Chlamys) is markedly less than that of other lamellibranchs and indicates the greater efficiency of the ligament of the former.

The mechanical properties of the isolated central region of the inner layer of the ligament of Pecten were investigated and showed similar properties to those of the intact ligament. The modulus of elasticity in compression of this region of the ligament of Pecten is approximately one-seventh of that of the inner layer of Ostrea or Lutraria, which are calcified structures. The ligament of the latter two bivalves has a greater opening moment but lower efficiency than that of Pecten. The characteristics of the ligament of Pecten are probably due to the central noncalcified region of the inner layer. The significance of these properties in regard to the swimming habit of Pecten is briefly discussed.
Central Nervous Function and Changes in Brain Metabolite Concentration
Authors: Chance M. R. A.
Published: April 2021

The changes in the glycogen content of different parts of the brain have been studied in mice in relation to the behaviour of these animals. Increases in glycogen content have been demonstrated after a jump, a fall, after the righting reaction accompanying a fall, and after aggressive behaviour has been shown in a fight. No increase has been demonstrated during sleep, after running or walking, or after defensive behaviour in a fight. It was shown earlier that external stimulation must reach convulsive intensity to produce an increase in brain glycogen, and it is suggested that the particular forms of normal behaviour associated with increase in brain glycogen involve a ‘convulsive’ type of brain activity. ‘Convulsive’ in this context may mean either a disturbance of the metabolism in some or all of the brain cells, or alternatively the mobilization of cell populations for simultaneous, and probably rapid, discharge. At present there is no evidence to suggest whether either or both of these possibilities are involved.
Enzymic Oxidation of Amines in Decapods
Authors: Blaschko H. , Himms Jean M.
Published: April 2021

Some time ago it was shown that a high concentration of the enzyme amine oxidase was present in the liver of Eusepia officinalis (Blaschko, 1941); it has since been found that this is also true for Octopus vulgaris (Blaschko & Hawkins, 1952a). In both species the enzyme occurs in other tissues as well as in the liver.
Studies on the Myoneural Physiology of Echinodermata
Authors: Pople Walter , Ewer D. W.
Published: April 2021

A myoneural preparation of Cucumaria sykion (Lampert) comprising a pharyngeal muscle and the corresponding radial nerve is described. A brief account is given of the histology of the preparation. Direct stimulation of the muscle gives a single response. Above fusion frequency the tension developed by the muscle increases with increasing intensity of stimulation, but it is unaffected by the frequency of stimulation. Stimulation of the radial nerve elicits a double response from the muscle. There is a ‘quick’ response which shows no myoneural facilitation and a ‘delayed’ response which shows a well-marked and prolonged facilitation. The tensions developed by both quick and delayed responses depend upon the intensity of stimulation applied to the radial nerve. Both responses show well-marked refractoriness at stimulation frequencies above about 10 stim./sec. It is suggested that the delayed response arises from the activity of the internmcial neurones in the motor complex, and that this is also the locus of the prolonged facilitation shown by the delayed response. The similarity of the properties of this system with certain features of the chordate nervous system are pointed out, but it is considered that any simple phylogenetic conclusions are unwarranted."
The Physiology of Contractile Vacuoles
Authors: Kitching J. A.
Published: April 2021

The contractile vacuole of the suctorian Discophrya piriformis Guilcher has been observed at hydrostatic pressures ranging up to 15,000 lb./sq.in. (1020 atm.). The rate of output of water was reduced at high pressures, and vacuolar activity was entirely suppressed at about 7000 lb./sq.in. (476 atm.). The vacuolar frequency was increased at 2000-3000 lb./sq.in. (136-204 atm.), but returned to normal on release of pressure. The frequency was depressed at 5000 lb./sq.in. (340 atm.) or more, but on release of pressure rose to a level higher than before treatment. The increase in vacuolar frequency at moderate pressures is perhaps comparable to the increase in tension of muscle at these pressures. High pressure probably promotes instability of the pore plug, and contraction and solation of the vacuolar wall.
The Mitotic Index and Interphase Processes
Authors: Walker P. M. B.
Published: April 2021

The mitotic index of a cell population, defined by Champy as the per mille proportion of the population in any mitotic stage, has long been regarded as an important criterion of the growth and multiplication of tissues. It is commonly measured in fixed and stained specimens, and therefore represents the stage of the material at the time of fixing only. However, cells grown in tissue culture may be observed and photographed for a considerable period before any measurement is made; such observations, which have been reported elsewhere (Walker & Yates, 1952a, b), show that some cytochemical results may require reinterpretation.
The Absorption of Water by Woodlice
Authors: Spencer J. O. , Edney E. B.
Published: April 2021

Experiments were undertaken to determine the site of water uptake, and the conditions in which it occurs, in Ligia oceanica, Oniscus asellus, Porcellio scaber and Armadillidium vulgare. Besides absorbing water with moist food, all four species were capable of active imbibition of water through both mouth and anus when a free water surface was available. In Ligia oceanica, imbibition occurred largely through the anus, in other species, through the mouth. Absorption through the anus was demonstrated by blocking the mouth by electro-cautery. All species save L. oceánica could imbibe water through the mouth from a damp surface (plaster of Paris) sufficiently rapidly to counteract the effect of transpiration from the integument in air at c. 85 % R.H. No water was absorbed through the anus in these conditions. The results help to resolve certain conflicting statements regarding the distribution of different species in the field. All species are for the most part ‘wet living ‘, but they differ as regards tolerance of suboptimal conditions.
A Note on the Pharmacology of the Dorsal Musculature of Peripatopsis
Authors: Ewer D. W. , Van Den Berg Roelof
Published: April 2021

As far as they have been studied the muscles of the body wall of annelids have been found to be sensitive to acetylcholine. The dorsal musculature of Hirudo medicinalis L. responds by contraction to a low concentration of the drug (Minz, 1932); among the chaetopods a similar effect has been shown with the body wall of Lumbricus terrestris L., Arenicola marina L. (Wu, 1939) and Branchiomma vesiculosum (Montagu) (Nicol, 1952). In all cases the threshold of response is at dilutions of 10−4 to 10−6. No such responses have generally been found with the skeletal muscles of the Crustacea. Bacq (1935) reports that the muscles of Carcinus maenas (Pennant) and Lepas anatifera L. do not respond to acetylcholine at a concentration of 10-4; du Buy (1935) was unable to elicit any response to crystals of the drug from the muscles of Cambarus sp.; Katz (1936) found no response from the muscles of Carcinus maenas to acetylcholine at a concentration of 10-5, but observed a ‘moderate short contracture’ to a concentration of 10-4;* Ellis, Thienes & Wiersma (1942) detected no response from the claw muscles of Cambarus clarkii Girard even at concentrations of 10-1.
The Excretory System of the Stick Insect, Dixippus Morosus (Orthoptera, Phasmidae)
Authors: Ramsay J. A.
Published: April 2021

The excretory system (Malpighian tubules and hindgut) of the stick insect is described, in extension of the earlier description by de Sinéty. Analyses have been made of the inorganic components of serum (haemolymph heat-coagulated and centrifuged), of urine (the fluid produced by the Malpighian tubules), of faeces, eggs and privet leaves. In the adult female insect most of the calcium ingested leaves the body with the eggs. The haemolymph has the characteristic mineral base pattern of the herbivorous insect; it appears to be supersaturated with magnesium phosphate. Its volume varies from 70 to 180 mm.3, with an average value of 130 mm.3, representing about 15% of the weight of the insect. The urine has the usual high concentration of potassium; except for phosphate the other inorganic components are present in lower concentration than in the haemolymph. Urine is produced at a rate of about 6 mm.3/hr., implying complete turnover of the water of the haemolymph every 24 hr. Except for a slight (20%) decrease in potassium concentration the composition of the haemolymph remains constant during fasting. The regulatory powers of the excretory system have been tested by injecting NaCl and KCl into the haemolymph and are shown to be relatively feeble.
Studies On the Myoneural Physiology of Echinodermata
Authors: Pople Walter , Ewer D. W.
Published: April 2021

The properties of a neuromuscular preparation of the mid-ventral pharyngeal retractor muscle of Cucumaria sykion (Lampert) have been previously described (Pople & Ewer, 1954). When excited by stimulation of the radial nerve, this muscle shows a double response consisting of a quick component, tentatively attributed to direct nervous paths through the motor complex of the muscle and a delayed component which possibly arises from secondary paths within the motor complex itself. This characteristic double response can be clearly seen in the contractions recorded in the upper trace of Fig. 2 of the present paper. The tension developed by this muscle is dependent upon the intensity of stimulation applied to the radial nerve. No evidence of frequency sensitive facilitation at the myo-neural junction was found.
Cutaneous Respiration in Woodlice
Authors: Edney E. B. , Spencer J. O.
Published: April 2021

Oxygen uptake and carbon dioxide output were measured in the woodlice Ligia oceanica, Oniscus asellus, Porcellio scaber and Armadillidium vulgare, in moist and in dry air, using normal animals and animals whose pleopods had been blocked by emulsion paint. In moist air, the rate of oxygen uptake which occurred through the general integument in animals whose pleopods had been blocked was about 50 % of normal in Ligia and Oniscus, but less than this in Porcellio and Armadillidium. After exposure to moving dry air, oxygen uptake in dry air was below normal in intact animals and nearly ceased in animals with blocked pleopods. Both showed a somewhat higher uptake if the oxygen tension was raised. Carbon dioxide output in moist air was not immediately inhibited by blocking the pleopods, suggesting free diffusion through the integument. Output fell during the first hour, but the R.Q. remained above 1 in all species. Survival times of blocked animals in moist air corresponded qualitatively with rates of oxygen absorption in the four species. In dry air survival was further curtailed, but prolonged again by an increased oxygen tension. Blocked animals of all species survived for a shorter time in moist nitrogen than in moist air. Injection of reduced indigo showed that oxygen was absorbed by intact animals through the thin ventral integument and bases of the legs in Ligia, and to a lesser extent, through the ventral abdominal integument in Oniscus and Porcellio. The ecological implications of these results are discussed, particularly with reference to the relation between survival and humidity. The dehydration death point is probably affected by the level of oxygen deficit and vice versa. A water-permeable integument is of value for respiration as well as for temperature control, but restricts the habitat range of terrestrial animals.
Factors Affecting the Temperature Excess of Insects in Sunshine
Authors: Digby Peter S. B.
Published: April 2021

The temperature excess developed by insects under known radiation strength equivalent to sunshine has been studied in relation to modifying factors in a wind tunnel in the laboratory. Temperature excess was measured by a thermocouple unit in the larger insects, and by the increase in rate of wing beat in Drosophila. Temperature excess varied directly with radiation strength. For insects of breadth greater than 0·3 cm. spectral composition of radiation over the normal sunshine range was of negligible importance to the temperature excess. The effect of colour on the temperature excess was slight. Absorptivity was estimated by comparing temperatures of normal and black-painted insects. Some insects were hotter in the normal state because of change in the site of absorption of heat. White-painted insects were 64−85 % as hot as when black painted, because the white paint still absorbs infra-red radiation. Temperature excess varied with a power of the size between 0·7 and 0·4 in the plasticine spheres, according to size. Temperature excess of the locust type varied as about the 0·4 power of the size ; of the Diptera-Hymenoptera type, as about the 1·0 power. Size for size, compared with the spheres, the locust became between half as hot again and twice as hot, and the Diptera-Hymenoptera type between half as hot again and three times as hot, as the plasticine spheres. Temperature excess varied inversely as the square root of the wind speed above speeds of 20−30 cm./sec. and tended to become independent at lower speeds, with the transition between forced and natural convection. The latter condition will be more important close to the ground. Temperature rise by flight activity is not additive to temperature rise from radiation because it is associated with extra cooling. Evolution of insects from the type of the Orthoptera to the Diptera and Hymenoptera has been associated with the attainment of greater temperature excess for given body size. This is probably of selective significance.
Ionic Regulation and Water Balance in the Aquatic Larva of Sialis Lutaria
Authors: Shaw J.
Published: April 2021

The electrolyte composition of the blood, tissues and excretory fluid of the aquatic larvae of Sialis lutaria has been measured, and the regulation of the concentrations of sodium, potassium and chloride in the blood studied in detail. In the normal larvae these ions are not present in the excretory fluid. Potassium and, perhaps, sodium are reabsorbed in the rectum but chloride is never present in the rectum. If these ions are present in the outside medium they are taken into the larvae through the gut. The blood concentration is regulated by the excretion of these ions via the rectal fluid. Potassium is rapidly excreted but chloride tends to be retained in the blood. Sodium is removed more rapidly than chloride. Water enters the larvae by osmosis through the cuticle, but can also be absorbed through the gut by osmosis or together with sodium ions. The water intake is balanced by excretion of rectal fluid. The factors affecting the rate of water excretion have been studied. The larvae are unable to survive in hypertonic saline solutions. This is due to their inability to make good osmotic water loss or to produce a hypertonic excretory fluid.
The Cortical Changes on Fertilization of the Sea-Urchin Egg
Authors: Kacser H.
Published: April 2021

The cortical changes which may be observed when the sea-urchin egg is fertilized have been the subject of a considerable number of investigations. The results have been discussed in relation to the problem of activation, and a number of conflicting views appear to be held at the moment. Three main lines of investigation give information on these processes. These are: (1) the kinetics of propagation in fertilized eggs, (2) artificial activation, and (3) the changes in mechanically constricted eggs. In what follows an analysis of the relevant evidence is presented. It will be suggested that a consistent picture of the nature of these processes can be given.
The Covering Reaction of Sea-Urchins
Authors: Millott Norman
Published: April 2021

Lytechinus variegatus (Lamarck) covers the parts of its skin that are exposed to light with fragments taken from its surroundings. The covering is taken up by the tube feet, assisted by the spines, and held in place by the tube feet acting in relays. It may be orientated with respect to the light source. There are indications of adaptability of behaviour where the covering pieces offer resistance to being lifted. Covering is related to light and to diurnal light changes, being assumed in strong light and rejected, after a varying interval of time, in darkness. Both continuous bright light and decreases in light intensity evoke covering. The tube feet react to the same stimuli and the speed of their extension is roughly proportional to the change of intensity. The tendency to cover is increased after a sojourn in darkness and is greater in pale individuals than in dark ones. Urchins can be photosensitized by injection of dyes so that they cover in dim light. The prehension and holding of covering does not involve the oral and aboral nerve rings. The relation of covering to light and environment favours the idea that it acts as a screen against strong light.
Studies in Diurnal Rhythms
Authors: Cloudsley-Thompson J. L.
Published: April 2021

The species of woodlouse investigated are known to stand in the following order as regards the rate of water loss by transpiration : Philoscia muscorum > Oniscus asellus > Porcellio scaber > Armadillidium vulgare. The intensity of the responses of the four species to humidity at room temperature (18+ 2° C.) are compared and are shown to stand in the same order. The intensity increases as desiccation proceeds.

At low temperatures (3 ± 2° C.) the intensities of the reactions to humidity are much reduced and are the same in all species; at higher temperatures (30 ± 2° C.) the humidity responses of Ph. muscorum and O. asellus are again somewhat reduced, and it is suggested that this may be correlated with a lower thermal death-point and the need to effect a reduction in body temperature by evaporation.

The antennal cone sensillae are shown to be contact chemo-receptors ; no specific sense organs are concerned with the appreciation of humidity. The response is correlated with saturation deficiency rather than with relative humidity and is probably engendered by dehydration. Ph. muscorum is the most strongly photonegative of the species and there is a graduation through O. asellus and P. scaber to A. vulgare which is the least so.

Ph. muscorum is also shown to be the most intensely nocturnal in habit, A. vulgare the least. It is therefore suggested that the degree of nocturnal activity is correlated with the ability to withstand water loss by transpiration. The results obtained are discussed in relation to the ecology of the species.
Further Observations on Co-Ordination and the Determination of Frequency in the Peristomial Cilia of Stentor
Authors: Sleigh M. A.
Published: April 2021

The work described is a continuation of the work on the peristomial cilia of Stentor previously reported (Sleigh, 1956). The same methods were used in making the observations. A cut across the peristome row of cilia did not affect the wave velocity, but the frequency distal to the cut was usually altered. In twenty-two cases the distal frequency was decreased, and in seven cases it was increased. Cilia in the gullet region are smaller and closer together than those in the main part of the row; these cilia show the same frequency as the other cilia, but a smaller wavelength and wave velocity. The number of cilia in every metachronal wave of the row is the same, as is the number of cilia stimulated in unit time by a single metachronal impulse in any part of the row. The wave velocity is dependent on the number of cilia through which the conduction is passed. The transmission is thought to be the result of a rapid conduction process between the cilium bases and a slower build-up of an excitatory state in the cilium. The frequency of a group of cilia is dependent upon the activity of a pacemaker at the beginning of the group; this pacemaker is probably a cilium with a suitable rate of beat. Frequency is limited by the rate of stimulation or the rate of contraction, whichever is the slower. It is suggested that there are some five excitation stages in the excitation of each cilium, and that each stage takes about 1 msec.; this is comparable with the delay at a nerve synapse. The results of these experiments and observations on ciliary activity indicate that the pacemaker and transmission properties of ciliated tissues and cardiac muscle are comparable in many respects.
Structure and Function in the Nematodes: Internal Pressure and Cuticular Structure in Ascaris
Authors: Harris J. E. , Crofton H. D.
Published: April 2021

No one who has made even a casual study of the Nematoda can fail to have been struck by the extraordinary similarity in form and organization between the very large number of species, genera, orders and families which constitute this class of the very diversiform phylum Aschelminthes. Though there are species which show some variation from the normal ‘nematode facies’, they are few in number and merely seem to emphasize still further the great uniformity of the group as a whole. The characteristic features of the nematodes are present in fresh-water, marine and parasitic forms; they are largely independent of size, of diet and of stage of development.
The Effect of Humidity on the Activity of Tsetse Flies
Authors: Bursell E.
Published: April 2021

Preliminary to an investigation of the water balance of tsetse flies some experiments were carried out to determine the effect of humidity on general activity. Observations previously made on this aspect of behaviour (Jack, 1939; Mellanby, 1936) have been too cursory to admit of general conclusions.
An Interferometric Method of Quantitative Analysis of Antigen-Antibody Reactions in Gels
Authors: Easty G. C. , Ambrose E. J.
Published: April 2021

A sensitive interferometric method of observing antigen-antibody complexes formed by diffusion of the reactants through gels in suitable diffusion cells is described. Bands of antigen-antibody complex, if not too dense, are observed as peaks in the interference fringes, the areas under the peaks being proportional to the quantities present in each band. The method may be made quantitative by measurement of the areas under the peaks of bands in which precipitation has not progressed too far, and by dissolving the bands of dense precipitate by diffusion of a suitable reagent to give peaks in the fringes. An equation expressing the quantity of precipitate present in a band has been derived.
The Relationship Between the Diurnal Light Cycle and the Time of Ovulation in Mice
Authors: Braden A. W. H.
Published: April 2021

The period required for the completion of ovulation in groups of mated females has been studied in 615 mice from three random-bred stocks (L, C and PCT) and in 137 mice of mixed origin. The mice were examined after having been kept for some time under one of four different diurnal light cycles, viz. the natural diurnal light cycle in Edinburgh in December (1) and in June (2) and artificial, reversed, light cycles of 10 hr. darkness/14 hr. light (3) and 4 hr. darkness/2O hr. light (4).

The variation between mice in any one group was greatest when they were maintained under the cycles that had a relatively long dark phase: a period of 12·14 hr. was required for ovulation in groups of L and C stock mice under cycles with a dark phase of 10·15 hr. whereas groups of similar females maintained under cycles with a 4·6 hr. dark phase required only 8·9 hr. for ovulation. Probit analysis indicated that this difference was statistically significant.

In changing the length of the dark phase of the diurnal cycle the beginning of each phase was altered by 3−412 hr.; the mid-points of each phase were altered by less than 1 hr. The results suggest that the mid-point of the ovulation period was determined more by the mid-point of the dark phase than by its onset or completion.

Differences noted between stocks of mice in the mid-point of the ovulation period and in the ability to adjust quickly to an altered light cycle gave indication that the neural mechanisms involved in the control of the time of ovulation in mice are modified according to the genetic constitution of the animal.

The mean interval between coitus and ovulation in females of L and C stocks under natural light cycles was found to be approximately 5 hr. The average time required for the ovulation of three-quarters of the total number of eggs shed in any one mouse (mean 11-12 eggs) was estimated as 0-5 hr.
Experimental Production of Midgut Tumours in Periplaneta Americana L
Authors: Harker Janet E.
Published: April 2021

Sub-oesophageal ganglia taken from Periplaneta americana L. which had been kept in reversed conditions of light and darkness have been implanted into the abdomens of cockroaches living in normal light: dark conditions. When implantation was continued for 4 days transplantable tumours appeared by the eighteenth day in the midgut of the majority of cockroaches. No tumours appeared in the guts of cockroaches when the implanted sub-oesophageal ganglia had been taken from animals kept in normal conditions of fight and darkness, nor when brains or corpora allata were implanted. Injection of an extract of five sub-oesophageal ganglia in 0·05 ml. Ringer solution produced tumours only when injection took place during the inactive phase of the 24 hr. locomotory rhythm.
The Co-ordination of the Responses of Cerianthus (Coelenterata)
Authors: Horridge G. A.
Published: April 2021

Cerianthus membranaceus, as commonly available at Naples, is a brownish polyp which can extend to 15–20 cm. and contract to 5–7 cm. The numerous tentacles are less contractile, being usually 3-5 cm. long. The gross anatomical structure is well described by Hyman (1940). The polyp normally lives in a soft tube, which it secretes, and has no foot or sphincter muscle. Lacking the diversity of muscle groups of a typical sea anemone its movements are very restricted. In contrast to other coelenterate polyps the Ceriantharia have a substantial ectodermal musculature of the column, which is responsible for the vigorous withdrawal of the animal into its tube. There are also ectodermal radial fibres on the disk. Endodermal muscles are relatively insignificant and play no part in the responses considered here. In common with all other coelenterate polyps Cerianthus has two kinds of rapid response to external changes: the feeding movements and the protective retraction. In Cerianthus the two are aroused by different stimuli, and in part they are effected by different muscles. The present study is an analysis of some of the physiological properties of the pathways which co-ordinate these responses.
Superpregnancy in the Mouse
Authors: McLaren Anne , Michie Donald
Published: April 2021

Superovulation was induced by gonadotrophin treatment in adult and immature female mice. The uteri of treated females and of control, naturally ovulating females were examined at 712 days post coitum by means of a laparotomy operation, and again at autopsy 1812 days post coitum. The mating rate of the two older groups of treated immature females was significantly higher than that of either the two younger groups or the treated adults. The proportion of mated females which became pregnant was low in the youngest group, but increased rapidly with age up to the control adult level. The mean number of implants per uterine horn in treated females in which implantation occurred was about twice that found in untreated control females, and did not vary with age. On the other hand, the variation in the number of implants per uterine horn was significantly greater among adult treated than among immature treated females. Total failure of pregnancy through death or disappearance of the embryos was most common among younger females with very large numbers of implants. Partial litter loss through death of individual embryos was greater in adult treated than in immature treated females. Combining partial and total litter loss, the gross mortality rate of embryos was independent of the age of the mother. Death of individual embryos before day 10 was more common in treated than in untreated females, and more common in adult treated than in immature treated females. The incidence bore no relation to the total number of implants either per female or per uterine horn, did not affect the survival of the remaining implants, and was not reduced by progesterone treatment. The death rate of individual embryos during the middle period of pregnancy did not significantly exceed the control level until the number in the horn rose above eight, at which point it increased abruptly in all treated groups. In the immature, but not in the mature, treated females the presence of more than eight implants in both horns was associated with still higher mortality. Death of individual embryos during the later part of pregnancy occurred relatively rarely and was associated with crowding of the uterine horn. In adult treated females which were allowed to go to term, the number of young born alive was inversely related to the number of embryos which had implanted. Our results are discussed with reference to the possibility of artificially increasing the reproductive output of mice and other mammals.
The Waterproofing Mechanism of Arthropods
Authors: Beament J. W. L.
Published: April 2021

The relationship between the temperature of the cuticle and its permeability to water has been determined for a number of different terrestrial arthropods. In most of these animals the waterproofing wax loses its great impermeability to water very abruptly at a particular transition temperature; that temperature varies appreciably with the individual, but appears to be characteristic of any one species at a particular age within a particular instar. No change in permeability with temperature was found in Tipula sp. taken from soil, in which the cuticle was greatly damaged ; above 48° C. the permeability of the cuticle of Schistocerca nymphs changes rapidly with increasing temperature, but this change is not abrupt. In the permeability/temperature curves for larvae of Pieris, Tenebrio, Calliphora and Nematus, pupae of Calliphora and adults of Schistocerca, Ixodes and Ornithodorus only one transition discontinuity is found. In all these animals the wax maintains almost constant permeability up to the point of transition, above which permeability increases very rapidly with temperature. Immediately after moulting, Rhodnius nymphs and pupae of Tenebrio and Pieris also reveal only one transition point; this occurs at a comparatively low temperature. But when cement is secreted over the primary wax layer, a second and higher transition point is found which is independent of the first point. The lower transition temperature seems constant in position during the life of an instar, but the upper point occurs at progressively higher temperatures as the instar ages. The evidence suggests that these animals have two special waterproof layers of wax, the one with high transition temperature occurring on the outer surface of the cement. This outer layer could arise by the migration of wax from the primary layer (with lower transition temperature) through the cement to the outer surface, there to lose volatile components and waterproof the surface. In every animal investigated a permanent increase in permeability is produced by heating a wax layer above its transition point; after such treatment no transition point can be found. From calculations of the absolute permeability of the various wax layers, and from the behaviour of the wax, it is suggested that all epicuticular waxes are laid down with some special molecular arrangement and that in very waterproof insects this may extend throughout the thickness of the wax layers; in less waterproof insects only a portion of the wax layer (as in the cockroach) may be specially organized. Very slight mechanical damage promotes increased transpiration through the cuticle. Stationary adsorptive dusts applied directly to a primary wax layer do not affect permeability; applied to wax above the cement, they promote rates of evaporation in excess of the value exhibited by the same cuticle having a primary wax layer alone. This phenomenon is discussed in relation to the distribution of water within the transpiring cuticle.