bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Cuvierian Tubules of Holothuria leucospilota
Authors: Endean R. 
Published: April 2021

ABSTRACT
Each Cuvierian tubule of Holothuria leucospilota consists of a bounding layer of large cells beneath which are bundles of fibres embedded in a clear ground-mass. Present also is an axial cavity containing a core of morula-shaped cells. Immediately below the outer layer longitudinal muscles occur and, internal to these, muscle-bands which run spirally are found.
The cells of the outer layer contain either granulated compartments or angular bodies. Both compartments and angular bodies contain proteinaceous materials. When a tubule is stretched in sea water the cells of the outer layer split and their contents form an amorphous mass which has strong adhesive properties.
The fibres present in the connective tissue of the tubules are collagenous and are associated with acid polysaccharides part, at least, of which are mucopolysaccharides. A polysaccharide which can be removed by testicular hyaluronidase is present in the interfibrillar ground-mass. The chemical constitution of the tubule connective tissue is similar in many respects to that of vertebrate connective tissue.
The mode of discharge and elongation of the tubules is discussed.
The Surface of the Sea-urchin Egg
Authors: Rothschild Lord 
Published: April 2021

ABSTRACT
Unfertilized eggs of the sea-urchin Echinus esculentus were fixed in potassium permanganate, sectioned, and examined under the electron microscope. A membrane consisting of an outer electron-opaque layer 84 Å wide, an electron-transparent layer 67 Å wide, and an inner electron-opaque layer 66 Å wide was observed at the egg surface. No other membrane or electron-opaque layer could be found anywhere within 4μ of the egg surface.
Integration in Aggregating Cellular Slime Moulds
Authors: Shaffer B. M. 
Published: April 2021

ABSTRACT
Cellular-slime-mould amoebae that adhere poorly to one another on contact and effectively do not secrete the chemotactic agent acrasin may become strongly adhesive and start to secrete it. This change, which is particularly important for their aggregation, has been called integration, and the reverse change, disintegration. In Polysphondylium violaceum a cell may receive the integrative stimulus at some distance from the acrasin source that attracts it, but usually it does not change till it has moved close to it or actually reached it; so either an aggregation is simply a heap without any tributary cell-streams, or virtually continuous streams are slowly built out from the centre. In Dictyostelium discoideum the spread of integration, in comparison with cell velocity, may be so rapid that the inflowing streams very soon reach their ultimate extent, though if the population density is not too high their cells only slowly establish contact with one another. As the peripheral cells become integrated, they ‘relay’ the centre’s influence. Whether the streams are uninterrupted or ‘stippled’, there need be no continuous and finely graded centrifugal decrement in acrasin secretion: orderly aggregation is ensured by the sequence in which secretion is induced, which results in the centrifugal propagation of one or more comparatively narrow zones in which the gradient is adequate for orientation. A spontaneous or an experimentally produced decrease in the strength of the integrative stimulus, or adaptation to the stimulus, or both, may induce some integrated cells to revert to the unintegrated state. The spread of disintegration, too, in comparison with cell velocity, tends to be more rapid in D. discoideum than in P. violaceum: in the former species all the cells in a considerable length of stream may begin to separate at almost the same time ; in the latter they may detach themselves in succession. As disintegration may affect any part of an aggregation, various patterns result therefrom. If it slowly spreads from the centre of a P. violaceum aggregation while the streams are still growing at their outer ends, a ‘fairy ring’ is formed, in which cell movement remains polar. Populations of a D. mucoroides strain, if not too sparse, aggregate at a comparatively fixed time after consuming the available food ; but those of D. discoideum at widely different densities and degrees of starvation produce synchronous outbursts of aggregation when transferred from darkness to light. The development and distinctive properties of the initiators of aggregation centres are considered. These cells can release acrasin into the medium without there being any there already or without there being sufficient to induce the remaining cells to secrete. Much evidence is against aggregation being basically a sexual phenomenon.
[Quarterly Journal of Microscopical Science, Vol. 99, part 1, pp. 103-121, Jan. 1958.]
The Spermatid of the House-cricket, Acheta domesticus
Authors: Clayton Blanche-P. , Deutsch K. , Jordan-Luke B. M. 
Published: April 2021

ABSTRACT
The spermatid of the house-cricket, Acheta domesticus, has been studied by the use of vital dyes, histochemical tests, and electron microscopy. The acroblast consists of an outer and an inner part. The former, which contains lipids and a neutral mucopolysaccharide, is seen in the electron micrographs to consist of parallel lamellae. In section these appear to be arranged in the form of a horseshoe. The internal part of the acroblast gives feeble reactions for a neutral mucopolysaccharide and for a lipid. In electron micrographs it is seen to contain minute vesicles. The acrosome arises within the acroblast. It gives a strong reaction for neutral mucopolysaccharide. It appears to be devoid of internal structure. The Nebenkern formed by the fusion of all the mitochondria in the young spermatid, exhibits the ‘cristae’ characteristic of ordinary mitochondria. The reactions of this structure with vital dyes and acid fuchsine also parallel those of the mitochondria. Histochemical tests indicate the presence of a lipid. The periphery of the nucleus of the late spermatid shows a radial structure.
The Absorption of Oleic Acid from the Small Intestine of the Rat
Authors: Hewitt W. 
Published: April 2021

ABSTRACT
By the use of histochemical techniques, the lipids (fatty acid, neutral fat, and phospholipid) were studied in the villi of the small intestine of the rat, 1 h and 2 ¾ h after feeding with oleic acid. The results of these experiments were identical with those previously described when triolein was administered. Neutral fat, fatty acid, and phospholipid were present in varying quantities within the cells. Between the cells and in their striated border, neutral fat and fatty acid were detectable. Within the cells, fatty acid was most abundant 1 h after feeding, whereas neutral fat and phospholipid predominated h later. The direct relationship between the amounts of neutral fat and phospholipid present in the cells, which had been observed in the studies with triolein, prevailed in the experiments described here.
The Formation of Tracheae and Tracheoles in Rhodnius prolixus
Authors: Locke M. 
Published: April 2021

ABSTRACT
The formation of tracheae in Rhodnius is described by the hypothesis of expansion and buckling. The cuticulin lining is at first a smooth-walled cylinder. Later it expands equally in each direction, increasing in diameter but buckling in the axis. An engineering expression describing symmetrical buckling in a cylinder under uniform axial compression has been applied to this process. Agreement was obtained between the expected and observed values for buckling frequency and tube-wall thickness. The taenidia are formed within the buckles, their amplitude being proportional to the increase in diameter. The axial orientation of the chitin micelles in the lining membrane and the tangential orientation in the taenidia are consjstent with their being oriented by the stresses expected during expansion and buckling. The formation of tracheoles may also be described by the expansion and buckling hypothesis.
Reactions between Egg-shell Matrix and Metallic Cations
Authors: Simkiss K. , Tyler C. 
Published: April 2021

ABSTRACT
The interaction between egg-shell matrix and various metal ions has been studied by considering the effect of these ions on the staining of the matrix by toluidine blue. The validity of the procedure and the influence of pH and various anions were tested. The main hypothesis to emerge was that the matrix acts as a chelating agent. Curves obtained when quantities of sodium hydroxide added to matrix were plotted against pH values were found to vary in position according to the absence or presence of cations and with different cations. This also supports the hypothesis that the matrix acts as a chelating agent. The significance of this in relation to the deposition of calcium carbonate as egg-shell is briefly discussed.
A Technique for Marking the Site of Recording with Capillary Micro-electrodes
Authors: Bultitude K. H. 
Published: April 2021

ABSTRACT
Records were made from the hind-brain of 15-cm tench (Tinea tinea, Osteichthyes) by the use of capillary micro-electrodes. At the completion of recording the electrodes were left in position and the site of recording was marked by the following method. The Ringer bathing the brain was replaced by a mixture of equal parts of 110 mM FeCl3 and Ringer. After 4 h, ferrocyanide ions were released electrolytically from the micro-electrode. The electrolyte in the micro-electrodes was 2·5 M KCl+0·5 M Na4Fe(CN)6. The optimum quantity of electricity for the electrolysis was found to be 2× 10-4 coulombs. The brain was then fixed overnight in 90% alcohol, sectioned at 20 μ, and stained with eosin.
Precipitates of Prussian blue about 20 μ, in diameter were found at the site of the electrode tip.
The Structure and Function of the Gas Bladder in Argentina situs
Authors: Fänge Ragnar 
Published: April 2021

ABSTRACT
Anatomical and histological observations were made on the gas bladder of the soft-rayed marine salmonoid fish Argentina silus, which usually lives at depths of about 200 m. The gas bladder is completely closed but rather unlike other known types of closed gas bladders. It is composed of three tissue layers, which may conveniently be called mucosa, submucosa, and tunica externa. The latter contains a large amount of guanine. The tunica externa is penetrated by numerous blood-vessels, which form a widely distributed rete mirabile of a peculiar ‘bi-dimensional’ type in the submucosa. All vessels reaching the mucosa seem to come from this rete system, and no special ‘resorbent mucosa’ such as occurs in euphysoclistae could be identified. The mucosa is folded, forming an alveolar-like structure of unknown function. The gas gland layer is separated from the lumen of the bladder by smooth muscles and an inner epithelium. The close anatomical association of the gas gland tissue with smooth muscles probably is of importance for gas secretion. Analyses of gases from specimens taken from a depth of about 80 m showed a mean oxygen value of almost 80%, which indicates a similar gas secretory mechanism to that in euphysoclistae. Certain aspects of the physiology of the gas bladder in relation to life in deep water are shortly discussed, and the need for a thorough histological examination of the gas bladder in deep-water salmonids is emphasized.
A Histochemical Study of Dehydrogenase Activity in the Pectoralis Major Muscle of the Pigeon and certain other Vertebrate Skeletal Muscles
Authors: George J. C. , Scaria K. S. 
Published: April 2021

ABSTRACT
Certain dehydrogenases in the breast muscle of the pigeon and fowl and the leg muscle of the fowl and frog were studied histochemically by the use of 2:3:5: triphenyl tetrazolium chloride. The dehydrogenase activity was found to have a relationship with the colour and the mitochondrial content of the individual muscle fibres. In the pigeon breast muscle, however, the broad white fibres did not show the presence of any of the enzymes studied. It is therefore concluded that these fibres in the pigeon breast muscle are a unique system in which none of the oxidative processes concerned takes place; they cannot be considered as analogous to the white fibres of the other muscles studied.
The Chromosome Numbers of certain Barnacles in British Waters
Authors: Austin A. P. , Crisp D. J. , Patil A. M. 
Published: April 2021

ABSTRACT
The chromosome numbers of nine species of sessile barnacles have been determined from squashes of young embryos stained by an iron alum aceto-carmine method. All the species of Balanus examined, and Elminius modestus had a diploid count of 32 chromosomes. Chthamalus stellatus and Verruca stroemia had each 30 chromosomes. Meiosis occurs after the egg passes into the mantle cavity, and the cytological changes accompanying the extrusion of the two polar bodies are figured.
The Cultivation in the Living Organism of the Thymus Epithelium of the Guinea-Pig and Rat
Authors: Grégoire CH. 
Published: April 2021

ABSTRACT
In autografts of thymus enclosed in porous cellulose membranes, the epithelium grows out in the shape of nodules, compact sheets, cords, and scattered isolated islands. During the experimental period, regeneration of the thymocytes did not take place in the grafts, provided that exogenous lymphocytes from other parts of the body were prevented by the cellulose barrier from penetrating the remnants of the thymic epithelium.
Light penetration into fresh water
Authors: Pearsall W. H. , Ullyott P. 
Published: April 2021

ABSTRACT
Potassium-on-copper vacuum photo-electric cells, in conjunction with a thermionic potentiometer and Unipivot galvanometer, have been found to be satisfactory for measuring sub-aqueous light intensities.
Some characteristic results indicate that the light intensity at the limit of sub-aqueous vegetation may be much higher than those recorded in corresponding terrestrial habitats. It is suggested that the quality of the light is of great biological importance.
Light penetration into fresh water
Authors: Pearsall W. H. , Hewitt T. 
Published: April 2021

ABSTRACT
During measurements of the penetration of light into water (4), evidence was obtained which suggested that the water of Windermere was less transparent in 1932 than it had formerly been. There were also indications that the depth distribution of vegetation in this lake had changed. It was, therefore, decided to repeat some measurements of light penetration and vegetation distribution which had been made in 1919-20 and in this way to obtain evidence of the apparent changes. The earlier measurements of light penetration were made by the iodide-sulphuric acid method, in which the light intensity is measured by estimating the amount of iodine liberated when a solution of potassium iodide mixed with sulphuric acid is exposed to the light. The same procedure was employed in 1932 as in the earlier experiments. Twenty cubic centimetres of 2 per cent, potassium iodide were mixed with an equal volume of 1-15 per cent, sulphuric acid (by weight) and were then exposed to light. After exposure, the iodine liberated was titrated with freshly prepared and standardised potassium thiosulphate, N/100 or N/1000 depending on the amount of iodine liberated. The solutions were exposed in conical flasks fastened by wire to a weighted line at fixed depths. The line was suspended from a small buoy, which had little or no shading effect at 1 m. The measurements were normally made in duplicate or triplicate at each depth, so that an average could be taken. Normally the solutions were exposed from 6 to 8 hours. The full light intensity was measured by exposing a series of successive similar solutions for from 1 to 2 hours each, during the whole time the submerged solutions were exposed. Two samples were kept in the dark, since the solution degenerates slightly in the dark during warm weather. The values for these dark controls were subtracted from all light readings. The results for sub-aqueous intensities were then expressed as percentages of the values for full daylight.
Studies on the growth of tissues In Vitro
Authors: Willmer E. N. 
Published: April 2021

ABSTRACT
A method is described by which hanging drop cultures of chick heart fibroblasts can be photographed at stated intervals for long periods of time. The growth of cultures in embryo extract has been analysed and the actual part played by outward migration of cells into the medium and by cell division has been evaluated. A formula is given for expressing the growth rate of a culture in terms of the percentage of cells dividing per hour. This is termed the growth index. Growth has been shown to occur uniformly, but at a decreasing rate for the first 36 hours and then to decline quickly and to become somewhat irregular. The actual number of cell divisions on the field in a culture in embryo extract reaches a maximum at about the 30th hour of cultivation, but is fairly constant from about the 20th to 36th hour. Cells divide most frequently near the periphery, where there is an optimum cell population density. The period of mitosis remains fairly constant throughout the growth of the culture, tending to increase when the culture is growing less rapidly at the end, when the cells may stay for a considerable time in metaphase. The intermitotic period is variable and increases greatly as the culture grows older. The effects of certain alterations in the composition of the medium are described. Dilution of the extract with Tyrode solution caused a considerable fall in the rate of cell division. The dilution of extract with serum instead of Tyrode solution produced a similar decrease in mitotic activity, but tended to increase the number of cells on the field. The independence of cell activity and cell division is stressed.
Airflow Sensors in the Avian Wing
Authors: Brown Richard E. , Fedde M. Roger 
Published: April 2021

ABSTRACT
Mechanoreceptors on or near feather follicles in the wings of birds may provide information about airflow over the wing. We studied discharge characteristics of rapidly and slowly adapting mechanoreceptors associated with propatagial covert feathers, slowly adapting receptors within the alular joint and vibration-sensitive receptors of filoplume follicles attached to the follicles of secondary flight feathers during manual feather movements and during airflow over the wing. Dorsal elevation of covert feathers produced an increase in discharge frequency related to the angle of elevation. Extension of the alula produced an increase in discharge frequency related to the angle of extension. Stimulation of receptors located on the distal half of the follicles of secondary flight feathers by airflow over the wing produced a continuous discharge whose frequency correlated with airflow velocity. There is thus abundant sensory input from the wing to the central nervous system. We conclude that birds have the necessary sensor-feather mechanisms in the wing (1) to detect an imminent stall and the location of the separation point of the airflow from the wing’s surface, and (2) to measure airspeed by detecting the frequency of vibration of the secondary flight feathers.
Ontogeny of Feeding Morphology And Kinematics in Juvenile Fishes: A Case Study of the Cottid Fish Clinocottus Analis
Authors: Cook Amy 
Published: April 2021

ABSTRACT
The development of feeding morphology, kinematics and behavior was examined in the juveniles of the cottid fish Clinocottus analis. The attacks of 18 juvenile C. analis, between 17.59 mm and 42.15 mm in standard length (SL), feeding on brown worms were filmed using high-speed video. Feeding mode, ram-or suction-dominated, kinematic variables and morphology were quantified and compared over the juvenile period. The analysis of these three factors was based on the following questions: (1) do they change over ontogeny; (2) how do their values compare with those of larvae, juveniles and adults of other species; and (3) what is the level of stereotypy, as measured by the variance in these factors, at this stage in ontogeny and does it change? Small C. analis juveniles have the small gape and large buccal cavity of a suction feeder, and this morphology becomes more pronounced as they become larger. The kinematic variables of C. analis juveniles are similar to those of adult suction-feeding cottids and least-squares regression analysis showed significant changes in only two variables (time to prey capture and absolute attack predator–prey distance) over the juvenile period. Feeding mode, as measured by the ram-suction index, shows an increase in the suction component of the strike with increasing size. This study demonstrates that, in C. analis, suction feeding behavior develops during the juvenile period. Within the juvenile stage, morphology, prey-capture kinematics and feeding mode are not tightly linked ontogenetically such that suction-feeder kinematics (short predator–prey distance and low attack velocity) and basic morphology (small gape, large buccal volume) develop much earlier than the employment of a large suction component during the strike.
Olfaction and Prey Search in the Carnivorous Leech Haemopis Marmorata
Authors: Simon Ted W. , Barnes Kevin 
Published: April 2021

ABSTRACT
Haemopis marmorata, the green horse leech, is carnivorous and readily eats earthworms. Using a Y-maze with flowing water, we show that specimens of H. marmorata are attracted to live earthworms. Ablating the dorsal lip, the presumed site of the chemoreceptors that this species uses in prey search, disrupts the ability of the leeches to find the earthworms in the Y-maze. Earthworm wash, a preparation of the collagen coating of earthworm skin, shock-induced earthworm secretion, mammalian blood and a salt–arginine mixture are not attractive to the green horse leech. The tails of freshly killed earthworms are attractive to the leeches, but tails from worms killed 8–12 h previously and stored cold are not. Our conclusion is that the earthworms produce a metabolite that attracts the leeches.
Ventilation and Gas Exchange in Lizards During Treadmill Exercise
Authors: Wang Tobias , Carrier David R. , Hicks James W. 
Published: April 2021

ABSTRACT
The extent to which lizards ventilate their lungs during locomotion is controversial. Direct measurements of airflow across the nostrils suggest a progressive reduction in tidal volume and minute ventilation with increased running speed, while other studies have demonstrated that arterial remains constant during exercise. To resolve these conflicting findings, we measured minute ventilation and gas exchange rate in five specimens of Varanus exanthematicus and five specimens of Iguana iguana during treadmill locomotion at speeds between 0.14 and 1.11 m s−1 at 35 °C. These speeds are much lower than maximal running speeds, but are greater than the maximal aerobic speed. In both species, the ventilatory pattern during locomotion was highly irregular, indicating an interference between locomotion and lung ventilation. In Varanus exanthematicus, treadmill locomotion elicited a six- to eightfold increase in minute ventilation from a pre-exercise level of 102 ml kg−1 min−1, whereas the rate of oxygen uptake increased approximately threefold (from 3.9 to 12.6 ml kg−1 min−1). After exercise, both minute ventilation and gas exchange rate decreased immediately. Because minute ventilation increased more than did oxygen consumption, an increase in lung during exercise is predicted and, thus, Varanus exanthematicus appears effectively to ventilate its lungs to match the increased metabolic rate during locomotion at moderate speed. In Iguana iguana, both minute ventilation and gas exchange rate increased above resting values during locomotion at 0.28 m s−1, but both decreased with further increases in locomotor speed. Furthermore, following exercise, both minute ventilation and oxygen uptake rate increased significantly. Iguana iguana, therefore, appears to be unable to match the increased oxygen demand with adequate ventilation at moderate and higher speeds.