bluuebunny/crossref_metadata_2025 huggingface dataset:
The cuticle of Peripatopsis moseleyi
Authors: Robson Elaine A.
Published: April 2021

The integument of Peripatopsis moseleyi has been examined by light and electron microscopy with particular reference to the structure and formation of the cuticle. The evidence supports the idea that Peripatus is a true arthropod but not that it has direct affinities with the annelids. The characteristics of arthropod cuticle are present in their simplest form and pore canals and dermal glands are lacking. The cuticle is 1 or 2µ thick except in the hardened claws and spines. Above the procuticle (chitinprotein) is a thin 4-layered epicuticle. It is possible that the innermost of the 4 layers (prosclerotin) may correspond to cuticulin of other arthropods. In the claws and spines tanning in this layer extends to the procuticle. Hydrofuge properties of the cuticle probably depend on the outer layers of epicuticle, and it is suggested that the lamina concerned might consist of oriented lipid associated with lipoprotein (Dr. J. W. L. Beament). Wax and cement are absent. Non-wettability of the cuticle is probably ensured by the contours of micropapillae which cover the surface. Similar structures arise in Collembola and other terrestrial arthropods by convergence.

The formation of new cuticle before ecdysis is described. After the epicuticular layers are complete, the bulk of the procuticle is laid down in a manner probably common to all arthropods. Secreted materials originate in small vesicles derived from rough endoplasmic reticulum and from scattered Golgi regions. The latter contribute to larger vacuoles which rise to the surface of the cell and liberate material in a fluid state. This later consolidates to form procuticle. Vesicles may also open to the surface directly, and ribosomes probably occur free in the cytoplasm. At this stage the cell surface is reticulate, especially under micropapillae.

The ordinary epidermis has only one kind of cell, attached to the cuticle by tonofibrils disposed like the ribs of a shuttlecock, and to the fibrous sheaths of underlying muscle-fibres by special fibres of connective tissue. These features and the presence of numerous sensory papillae are associated with the characteristic mobility of the body wall. The appearance of epidermal pigment granules, mitochondria, the nuclear membrane, and a centriole are noted. No other cells immediately concerned in the formation of cuticle have been found. By contrast myriapods, which do not have wax either, possess dermal glands secreting far more lipid than is found in the Onychophora. The wax layer found in insects and some arachnids constitutes an advance of high selective value which emphasizes the primitive condition of the Onychophora. It is noted that the thick layer of collagen separating the haemocoel from the epidermis probably restricts the transfer of materials. It is suggested that since some features of cuticular structure and formation appear to be common to all arthropods, it is possible that some of the endocrine mechanisms associated with ecdysis may also be similar throughout the phylum.
The structure of the unpaired ventral nerves in the blowfly larva
Authors: Osborne M. P.
Published: April 2021

The anatomy and histology of the unpaired ventral nerves are described from light- and electron-microscopical studies. Seven unpaired nerves arise from the median dorsal surface of the ventral ganglionic nerve-mass, and terminate in abdominal seg- ments 2 to 8 respectively. Each unpaired nerve bifurcates, sending a lateral nerve to both sides of its respective segment. Subsequently the lateral nerve gives rise to 2 nerve-branches. The first branch runs to a multipolar neurone that is associated with the tracheal system, and the second branch passes beneath the ventral longitudinal muscles and terminates on a ventral transverse muscle. Structurally, the unpaired nerve consists of axons ensheathed by Schwann-cells, the cytoplasmic processes of 2 giant Schwann-cells forming the entire neurilemma sheath of the nerve and its branches. A basement membrane, or connective-tissue sheath, about 2 p. thick surrounds the Schwann-cells. Four nerve-fibres are found in the unpaired nerve; 2 of these bifurcate, sending a fibre into both lateral nerves, but the other 2 fibres pass without dividing, into the left and right lateral nerves respectively, making a total of 2 fibres in both lateral nerves. One fibre from the lateral nerve enters the nerve- branch leading to the multipolar neurone associated with the tracheal system, and eventually joins its cell-body. This fibre is the axon of the neurone. The remaining 2 fibres in the lateral nerve pass into the nerve-branch that runs to the ventral trans- verse muscle. A comparison is made between the unpaired nerves of the blowfly larva and those in other insects.
Semper’s organ, a cephalic gland in certain gastropods
Authors: Lane Nancy J.
Published: April 2021

Semper’s organ has been studied and compared in two genera, Limax and Helix. In both cases the organ, which lies on each side of, and beneath, the buccal mass, is composed of glandular elements surrounding ganglia; the latter originate from two nerves arising from each side of the cerebral ganglia. In both, the organ produces the external swellings that form the mouth lobes on each side of the head. The chief difference between the two is that Semper’s organ is much larger in Limax. In Helix it is reduced to strands of secretory and nervous tissue, dispersed among abundant muscle-fibres.

In H. aspersa the glandular area surrounding the ganglionic part of the organ is composed of three cell-types. The cytoplasm of the chief cellular component, ‘Semper’s’ cells, contains a number of lipochondria, some of which possess the cortex of concentric lamellae typical of phospholipid globules. The cytoplasm of the second cell-type, or ‘mucus’ cell, is filled with electron-lucent globules between which are scattered electron-dense bodies that contain some polysaccharide and lipid. The third cell-type, the reticulate cell, is rather similar to the mucus cell, except that its cytoplasm contains a reticulum formed by strands which lie within, or applied to, the electronlucent globules; these cells contain acid mucopolysaccharides. The structure of the mucus and reticulate cells bears certain resemblances to secretory cells in the sheath of the optic tentacles in the same species.

The function of Semper’s organ is discussed. Certain evidence suggests that some of its secretory cells may have an endocrine activity, and the significance of lipochondria in such actively secreting invertebrate cells is considered.
Serial sectioning of refractory locust eggs
Authors: Anderson D. S.
Published: April 2021

A technique is described for sectioning the yolky tissue of locust eggs. It is a modified version of a method evolved by Griffiths and Carter and successfully used on reptile eggs. The fixative is dioxan saturated with picric acid, with 5% formic acid and 10% formaldehyde. It rapidly penetrates the yolk and minimizes hardening. Dehydration in cellosolve is followed by clearing in benzene. After embedding in wax the block is immersed in 5% tergitol ethane-diol solution, and 12 h later good serial sections are obtained.
Spittle-production and tube-building by cercopoid nymphs (Homoptera). 2. The cytology and function of the granule zone of the Malpighian tubules of tube-building nymphs
Authors: Marshall A. T.
Published: April 2021

The proximal segment of the nymphal Malpighian tubules of tube-building cercopoids consists of two secretory zones, an anterior fibril zone and a posterior granule zone. Cytological changes in the latter are correlated with the production of spittle before each ecdysis. Granules are present in the cells during inter-ecdysal periods. Shortly before spittle-production and ecdysis, coalescence of the granules occurs, followed by cytoplasmic vacuolation and the subsequent liberation of coalesced material into the tubule lumen.

The granule zone is essentially similar to the whole of the proximal segment of the Malpighian tubules of spittle-bug nymphs, although much smaller in length and cross-section. This is consistent with the reduced spittle-producing requirements of tube-building nymphs.
The Cytoplasmic Components of Germ-cells during Spermatogenesis in the Domestic Fowl
Authors: Zlotnik I.
Published: April 2021

1. The Golgi material of the maje germ-cells of the domestic fowl is in the form of a localized body, composed of rods and granules which lie on the surface of the archoplasm.

2. During the maturation divisions the localized Golgi material breaks down and forms a number of granules and rods which become dispersed at the beginning of the metaphase. After each division the scattered Golgi elements reassemble in the daughter cells and become once more attached to the archoplasm.

3. After the formation of the acrosome the Golgi material migrates to the residual cytoplasm and, as the Golgi remnant, is eliminated.

4. Accessory bodies are present in the cytoplasm of the spermatocytes from both silver and chrom-osmium preparations; in the spermatids only argentophil bodies are identified. One argentophil accessory body ‘Golgi X’ is included in the neck region of the spermatozoon.

5. The acrosome is formed from the proacrosome; the latter originates within the archoplasmic vacuole inside the Golgi material of the spermatid. The acrosome occupies the anterior tip of the head of the spermatozoon, and is conical in shape.

6. The nuclear ring is present in the early stages of the metamorphosis of the spermatid ; with the elongation of the nucleus it disappears.

7. The mitochondria are described during all the stages of spermatogenesis ; their ultimate fate is the formation of the mitochondrial sheath of the middlepiece. This sheath often appears in the form of a spiral structure.

8. During the transformation of the nucleus a coiled stage is constant ; this is due to the continuous elongation of the nucleus and lack of response from the cytoplasm. The head of the spermatozoon is an elongate worm-like structure.

9. Two centrioles are present in the spermatids of the domestic fowl. The axial filament originates from the two centrioles. The proximal centriole is attached to the posterior end of the head of the spermatozoon, while the distal centriole assumes the shape of a ring and marks the distal limit of the middlepiece.

10. A clear zone surrounds the posterior part of the nucleus of the late spermatid ; this zone possibly takes part in the formation of the middle-piece.
On the Functional Morphology of the Alimentary Tract of Some Fish in Relation to Differences in their Feeding Habits: Anatomy and Histology
Authors: Al-Hussaini A. H.
Published: April 2021

The mouth is larger and more protrusible in Gobio and Cyprinus than in Rutilus, features which may be associated with the mud-grubbing, bottomfeeding habits of the two former fish, while the arrangement of the adductor muscles in Rutilus enable it to close its mouth more quickly than they and hence it can rapidly snap up its free-moving prey. The selection of food is largely by taste in Gobio and Cyprinus, and hence both are richly supplied with taste-buds from lips to oesophagus, special concentrations being present on barbs around the mouth. Rutilus, on the other hand, augments taste by sight. Taste-buds are accordingly more restricted in distribution and less abundant where they do occur. They are fewer on the lips ; there are no barbs. The relative development of the pharyngeal masticatory apparatus (horny pad, pharyngeal teeth) bears a direct relationship to the amount of plant food in the diet, i.e. it increases in the order Gobio, Rutilus, Cyprinus. The mucus-secreting cells attain their maximum development in the pharynx in all three fishes, as is usual amongst teleosts (cf. Al-Hussaini, 1947a, p. 278) and are thus effectively placed to lubricate the food, irrespective of its nature, at the very commencement of its journey through the gut. Gill-rakers carrying taste-buds and mucus-secreting glands are present in all three fish, but they are exceptionally short in Gobio for a bottom-feeding fish. This may be compensated for to some extent by a pair of food-selecting palatal cushions. All three fishes are stomachless, the short oesophagus joining the pharynx directly to the pyloric sphincter. The loss of the food-holding capacity of the stomach is compensated for by the swelling of the first limb of the intestine. The intestinal tube is longest and its looping most complex in Cyprinus, and shortest and with the simplest looping in Gobio. Four parts are recognized in the intestinal tube, not by external features, but by their mucosal foldings and certain histological characters. An estimation of the mucosal area shows that the absorptive area of the intestinal epithelium is practically equal in the three species when related to the weight of the fish. This ratio has here been called the ‘mucosal coefficient’. The intestinal epithelium comprises two principal histological cell types, viz. the absorptive cell and the goblet cell. The internal surface across which food substances pass from the cells to the tissue fluids is greater in Cyprinus and Rutilus than in Gobio, owing to the greater length of the absorptive cells. In order to be valid, estimations of the relative efficiency of the fish intestine should take into account the relative length of the gut (R.L.G.), the mucosal coefficient (Q.M.), and the length of the absorptive cells.
A Description of a new Zooplankton Counter
Authors: Ward James
Published: April 2021

The new plankton-counting cell is an annular groove machined in a circular plate of lucite. The plate is mounted on a turntable and driven at a rate of about one revolution in six minutes. Counting is done by observation of the rotating sample as it moves through the field of a microscope. This apparatus provides the convenience of the ‘trough and flow systems currently used and has the advantage of being a more compact unit.
Adaptation to rock boring in botula and lithophaga (lamellibranchia, mytilidae) with a discussion on the evolution of this habit
Authors: Yonge C. M.
Published: April 2021

All species of Botula and of Lithophaga live within borings they excavate in rock, In Botula boring is mechanical, into soft non-calcareous rocks. Firm attachment is made by byssal threads arranged in a large anterior and a small posterior group. The rock is abraded by the dorsal surfaces of the valves, which are deeply eroded ; the forces responsible are contraction of the byssal and pedal retractors and the powerful opening thrust of the long ligament. There is no rotation within the boring. In Lithophaga boring is confined to calcareous rocks, byssal attachment being weak and the valves little eroded. The fused inner lobes of the mantle edges may protrude from between the valves anteriorly. They are applied to the head of the boring and it is postulated that they secrete an acid mucus. Some species of Lithophaga bore straight into rock, others rotate in the boring.

Aggregations of foreign particles on the valves of Botula and Lithophaga are due to the effect of accumulations of mucous glands both anterior and posterior to the ligament. The origin and function of these glandular masses is discussed by reference to conditions in the allied Modiolus. They help in disposing of sediment. In Lithophaga the anterior glands, at least, probably secrete an acid mucus. Crystalline calcareous secretions which adventitiously lengthen the shells of certain species of Lithophaga are produced by the walls of the siphons, which may also lay down a calcareous lining to the boring.

Evolution of the boring habit in the Mytilidae is discussed in relation to shell-form. The elongate shell of the dimyarian types Botula and Lithophaga is compared with those of Ensis or Tagelus and shown to be derived from that of a heteromyarian ancestor not unlike Modiolus. The effect of the tangential component in the growth of the mantle/shell counteracts that of reduction of the anterior end of the body and of the mantle/shell associated with heteromyarianism and is also concerned with lengthening of the ligament. Change in form in the Mytilidae made possible change in habit.
The Nervous System of the Ephyra Larva of Aurellia aurita
Authors: Horridge Adrian
Published: April 2021

The rapid co-ordination of the beat had been identified with a specialized system of neurones which spreads over the muscles from the marginal ganglia. By analogy with other invertebrates this has been called the giant fibre system.

The feeding response and the spasm are co-ordinated by a separate net, called ‘the diffuse nerve-net’, which is both physiologically and histologically distinct from the giant fibre system.

The histological structures of the two nerve-nets and the marginal ganglia are described.

Although the diffuse nerve-net contains sensory cells, it also acts upon the muscles, and a double motor innervation is indicated.

The two nerve-nets meet and interact at the marginal ganglia. An attempt has been made to interpret the neurone structure of the ganglia.
Cone Arrangements in Teleost Retinae
Authors: Lyall A. H.
Published: April 2021

There are four types of cone elements in teleosts : single, double, triple, and quadruple cones. The latter two types have only been found as typical elements in minnow (Phoxinus laevis) retinae. The constituent parts of a multiple cone may differ from each other in staining properties and size. A regular arrangement of single and double cones is a feature of many teleost retinae, but these cone patterns are only associated with equal double cones. Changes in the cone patterns occur during growth of the retinae. In trout (Salmo trutta) the pattern in young eyes has many more single cones than that in adult retinae. The loss of these single cones is probably due to their transmutation into rods. The derivation of the typical cone arrangement in central regions of the retina from that found at the periphery has been studied in trout, minnow, and pike (Esox lucius). In all these species there is a similar basic cone pattern at the edge of the retina, although the arrangements in more central parts are very different. It appears that the triple and quadruple cones in minnow retinae are formed by the fusion of a single cone with a double cone and a triple cone respectively.
The Cuvierian Tubules of Holothuria leucospilota
Authors: Endean R.
Published: April 2021

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Energetics of Swimming by the Platypus Ornithorhynchus Anatinus: Metabolic Effort Associated With Rowing
Authors: Fish F. E. , Baudinette R. V. , Frappell P. B. , Sarre M. P.
Published: April 2021

The metabolism of swimming in the platypus Ornithorhynchus anatinus Shaw was studied by measurement of oxygen consumption in a recirculating water flume. Platypuses swam against a constant water current of 0.45–1.0 m s−1. Animals used a rowing stroke and alternated bouts of surface and submerged swimming. Metabolic rate remained constant over the range of swimming speeds tested. The cost of transport decreased with increasing velocity to a minimum of 0.51 at 1.0 m s−1. Metabolic rate and cost of transport for the platypus were lower than values for semiaquatic mammals that swim at the water surface using a paddling mode. However, relative to transport costs for fish, the platypus utilized energy at a similar level to highly derived aquatic mammals that use submerged swimming modes. The efficient aquatic locomotion of the platypus results from its specialised rowing mode in conjunction with enlarged and flexible forefeet for high thrust generation and a behavioral strategy that reduces drag and energy cost by submerged swimming.
The Energy-Sources in Ontogenesis
Authors: Needham Joseph
Published: April 2021

In the foregoing papers of this series (19, 20,21,22) experimental data have been brought forward dealing with the nitrogenous excretion of the chicken embryo during its development in the egg. From studies of the ammonia, urea, and uric acid excretion, it was possible to calculate the amount of protein burnt every day, and as a result it was shown that a high peak of protein combustion existed about the ninth day of development. A systematic examination of the other papers in the literature brought out a powerful correlation between carbohydrate combustion and the earlier period, and between fat combustion and the later period. There thus appeared to be a succession of energy-sources in ontogenesis, carbohydrate preceding protein, and protein preceding fat.
Olfaction and Vision in Fish Schooling
Authors: Hemmings C. C.
Published: April 2021

The behaviour of individual roach was observed in a horizontal linear gradient of species odour. No attempt was made to analyse the odour involved. The behaviour of roach, grey mullet and Chromis was studied in the presence of (a) a mirror, or (6) a second fish behind a clear plastic sheet. Roach showed nearly as strong a response to attractant species odour as to the repellent ‘Schreckstoff’. The relative strengths of responses to directional visual images and non-directional odour gradients were compared. Short-term and long-term declines in the strength of the response to odour occurred. Observation of a ‘two-fish school’ suggested that a system of exploratory, returning and following tendencies co-ordinated schooling behaviour. Isolation of roach for a period of 20–25 weeks caused enhancement of the olfactory reaction but completely disrupted the visual response. It is suggested that school structure is maintained by balanced attractive and repulsive ‘forces ‘; the attraction modalities involved are vision by day and olfaction by night, and the repulsion modality is the lateral line sense.
Reflexes Mediated by Non-Impulsive Afferent Neurones of Thoracic-Coxal Muscle Receptor Organs in the Crab, Carcinus Maenas
Authors: Cannone A. J. , Bush B. M. H.
Published: April 2021

A preparation of the thoracic-coxal muscle receptor organ of the posterior leg of the shore crab, in which central synaptic efficacy of the sensori-motor reflex pathways is maintained for long periods, is described. The reflex response to receptor muscle stretch commonly involves three promotor motoneurones, designated Pm 1–3 in order of their recruitment. Motoneurone Pm1, and less frequently Pm2 and Pm3, may be tonically active during maintained receptor length changes within the in situ length range of the receptor muscle. The following observations suggest that the T rather than the S sensory fibre provides the afferent drive onto reflexly activated promotor motoneurones: selective section of the S or T sensory fibres; frequency ‘envelopes’ of individual motoneurone responses to trapezoid stretch stimuli, including features such as adaptation and velocity sensitivity of the reflex response; and the ‘hysteresis’ in the response to increasing followed by decreasing receptor length changes, with or without superimposed trapezoid stretch stimuli. The initial reflex response to ramp stretch can be directly related to the complex ‘initial component’ of the T fibre receptor potential waveform. This comprises a variable spiky alpha (α) component, followed by a longer duration, more predictable beta (β) component, which depends upon stimulus parameters such as stretch velocity and the length and tension of the receptor muscle at the onset of stretch. In the de-efferented receptor muscle, changes in compliance or ‘tonus’ resulting from receptor manipulation have a marked effect on the sensory, and hence reflex, response to stretch. As this would have profound implications for the functioning of this muscle receptor organ in vivo, a role for the receptor motor innervation in counteracting any such response variability seems likely.