bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Microscope Studies of Living Blood-cells of the Tunicates under Normal and Experimental Conditions, with a Description of a New Type of Motile Cell Appendage
Authors: Andrew Warren
Published: April 2021

The living blood-cells of tunicates have been studied by means of phase contrast microscopy. The species used were Ascidia atra Lesueur, Ecteinascidia turbinata, and Clavelina picta, all of which are common in the Bermuda region. Blood-cells in blood taken directly from the heart, or from the vessels, or elsewhere, particularly in the tunic of Ecteinascidia turbinata and Clavelina picta, were observed for periods ranging up to 24 h.

A new type of appendage is described for those cells which we have called vacuolate cells (‘Q cells’ of Fulton, ‘signet-ring’ and ‘colorless morula cell’ of George). Individual cells show from 1 to 5 appendages, which are beaded and actively undulate. Fragments from the appendages continue to undulate. Such fragments bear some resemblance to blood-platelets of higher vertebrates in their strongly adhesive properties.

In view of the morphological features, motility characteristics, and apparent functions, the terms lymphocyte and macrophage are considered appropriate for the finely granular and coarsely granular amoebocytes. No active swimming motions of the orange cells, nor of any other corpuscles were seen; but all of the types of cells, coloured and colourless, with the exception of the vacuolate cells, exhibit amoeboid progression.

No transformation of vacuolate into green cells was brought about in our experiments with varying strengths of acid, contrary to the earlier findings of Fulton. Many types of blood-cells in the tunicates have ‘fixed cell’ counterparts in the tissues. It is suggested that the large ‘bladder cells’ of the tunic of A. atra Lesueur may be such counterparts of the vacuolate cells of the blood.
The Shell of Acridid Eggs
Authors: Hartley J. C.
Published: April 2021

The shell of the newly-laid egg of Locusta migratoria is composed of a chorion and an outer layer, here termed the extrachorion. The development of the chorion and extrachorion has been followed. The structures of the egg-shells of Schistocerca gregaria, Ramalea microptera, and 6 species of British grasshoppers are also described and are found to conform to the same pattern. The chorion has a meshwork structure which may be filled with air or water. Wound repair in the eggs is also noted.
The Development of the Polychaete Haploscoloplos fragilis
Authors: Anderson D. T.
Published: April 2021

The eggs of Haploscoloplos fragilis, laid in gelatinous cocoons, develop as yolky trochophores which add 4 segments before hatching on the 6th day and two more during a pelagic phase before settling and the onset of feeding on the 10th day. The 6 (embryonic) segments bear a metatroch and 5 amphitrochs. The embryo also has an akrotroch, prototroch, telotroch, and neurotroch. All cilia disappear after settling, when the embryo shows resumption of segment formation. Anterior to the first trunk segment lie the prostomium and mouth region. The latter becomes subdivided by an annulus, but later fuses with the first trunk segment as the peristomium. All other segments become chaetigerous, the 5 embryonic being of thoracic type, the postembryonic abdominal. At the posterior end of the body lies the pygidium, with the segment-forming growth zone immediately in front of it.

The development of trunk segments in two series, embryonic and post-embryonic, is characteristic of ariciids, as is the fusion of the first trunk segment with the mouth region to form the peristomium. It is possible that the mouth region incorporates at least one other cephalized segment.

Ariciid eggs vary in size among species. No direct relationship exists between egg size and pelagic development. The mode of oviposition also varies. Whether or not a pelagic phase occurs depends on the stage at which the embryo becomes free in the water, which is governed in turn by properties of the cocoon (e.g. jelly viscosity). A pelagic phase is always associated with enhanced ciliation, while in non-pelagic development ciliation is reduced. The basic ciliation (akrotroch, prototroch, metatroch, telotroch, and neurotroch) is usually supplemented by additional segmental bands.
Some Aspects of the Cytology of Polycelis nigra
Authors: Skaer R. J.
Published: April 2021

The triclad, Polycelis nigra, has been found to be fully cellular. Gland-cells, undifferentiated cells, and the cell-bodies of muscle-cells, make up the parenchyma. The fine structure of the component cells of the parenchyma, nervous, and excretory systems, testis, pharynx, and epidermis is described. Acidophil secretion granules, produced by certain parenchymatous gland-cells, have a characteristic, doubly-banded ultrastructure which is not invariably associated with the property of adhesiveness. The parenchymatous cell-body of the muscles is often up to 10 μ from the musclefibre, to which it is joined by tenuous cytoplasmic connexions. The muscle-fibre itself consists of coarse and fine sets of hexagonally arranged myofilaments, but is unbanded. The basement membrane of the epidermis is composed of fine, banded fibrils, apparently randomly arranged in the plane of the membrane. Permeating the epidermis at a level just above the basement membrane is a system of extracellular spaces, which may have a hydrostatic function and assist in the extrusion of secretion granules. Epidermal sense organs, whose fine structure resembles the basal body of the cilia, are considered to have a functionally significant distribution on the surface of the animal. The rhabdites have been shown to develop in special cells of the parenchyma. Such rhabdite-forming cells, together with their contained rhabdites, have been found apparently passing through the basement membrane of the epidermis. As all the epidermal epithelial cells contain rhabdites, it is suggested that the epidermis as a whole is renewed by centrifugal migration of rhabdite-forming cells. The rhabdites themselves appear to consist of arginine and some tyrosine, together with a purine, probably adenine. They may be an excretory product.
The Development of the Malpighian Tubules in Dysdercuskoenigi (Hemipt er a, Pyrrhocoridae)
Authors: Srivastava U. S. , Bahadur I.
Published: April 2021

Dysdercus koenigi has two pairs of Malpighian tubules, each pair arising from a vesicle and forming a closed loop. The vesicles are connected dorsally, and the tubules are differentiated into proximal and distal regions with refractive granules in the latter and brush border in both.

In winters at Allahabad the embryonic period lasts about a fortnight, and on the 9th day, 4 small buds arise apparently from the anterior end of the proctodaeum. These grow rapidly and become tubular; their tips fuse, but the lumina remain separate. At this stage the met-enteric membrane (Henson, 1946a) stretches over the anterior end of the proctodaeum and an interstitial ring is differentiated, so that the zone of the origin of the tubules lies anteriorly to it and posteriorly to the met-enteric membrane. Meanwhile the basal part of each tubule swells and the two swellings of each side fuse, thus forming a vesicle on each side. A dorsal outgrowth from each vesicle meets its fellow of the opposite side. The tubules continue to elongate, at the same time becoming narrower, and ultimately only 3 cells can be seen in a cross-section. The tubules grow in 3 phases—(1) active mitosis, (2) of cell multiplication and cell rearrangement, and (3) of cell rearrangement and cell enlargement. Finally, the tips of each pair fuse completely and their lumina become continuous.

In the newly hatched first nymph the tubules are uniform throughout, but in the later part of this stage they become differentiated into proximal and distal regions and the striated or brush borders appear. Thus the embryonic development continues for some time in the first nymph. Once this condition has been reached, cyclical changes involving increase in the diameter of the tubules, in the size of the nuclei, and in the number of cells in the proximal region occur in each nymphal stage, but before each ecdysis the diameter decreases slightly. Thus the adult condition is reached in 5 distinct steps, corresponding to the 5 instars.

Henson’s view that Malpighian tubules are endodermal is considered plausible, but his view regarding the primitive number of tubules is not accepted.
The Histochemistry of the Radula of Patella vulgata
Authors: Runham N. W.
Published: April 2021

When first secreted the radula consists of chitin and protein. In the bases and cusps of the teeth the reactions for tyrosine, tryptophane, and chitin become negative, and are replaced by reactions for amino groups and argentaffin material. The bases of the teeth become impregnated with iron. Subsequently the reactions for amino groups and argentaffin material become negative in the cusps and they then become impregnated with iron and silica. Very few changes have been observed in the radular membrane.

It is suggested that the occurrence of quinone tanning might account for these histochemical changes observed in the radula, but phenols derived from tryptophane would appear to be more important in the tanning of the radula than those derived from tyrosine.
Tyrosinase Activity in the Pigmented Cells of the Nucleus Substantiae Nigrae. I. Monophenolase and Diphenolase Activity
Authors: Marsden C. D.
Published: April 2021

The method of formation of black pigment in cells of the nucleus substantiae nigrae has been investigated by employing histochemical techniques which detect tyrosinase, the enzyme responsible for melanin formation in skin melanocytes. Frozen sections of the mid-brains of adult monkeys and cats were incubated in L-tyrosine, to detect the monophenolase activity of tyrosinase; other sections were incubated in L-dopa to detect the diphenolase (dopa oxidase) activity of the enzyme. The dopa, but not the tyrosine, was converted into melanin by the cells of the nucleus substantiae nigrae, resulting in blackening of the cytoplasm.

The intensity of blackening of nigra cells resulting from incubation in L-dopa depended on physical factors. The optimum pH of the reaction ranged between 6·8 and 7·4; the optimum temperature was 37° C; the concentration of substrate employed and the duration of incubation were additional factors which influenced the intensity of the reaction. The conversion of dopa to melanin by nigra cells was prevented by general enzyme inhibitors and by specific inhibitors of tyrosinase, which confirmed the specificity of the reaction for the diphenolase activity of tyrosinase.

The significance of the presence of diphenolase activity, in the absence of monophenolase activity, in adult nigra cells has been discussed in relation to pigment formation in the brain.
Some Modifications of Holmes’s Silver Method for Insect Central Nervous Systems
Authors: Blest A. D.
Published: April 2021

Two main modifications of Holmes’s method are described. In both the amount of silver nitrate in the impregnating bath is increased, and larger quantities of higher pyridine derivatives are substituted for pyridine. The preferred method for general purposes employs 2· 4% 2:6 lutidine at pH 8· 4, and gives a bluish picture with improved selectivity of fibre staining. The use of 1 · 6% 2:4:6 collidine gives a reddish picture, with highly selective fibre staining, and sharp resolution of neurosecretory cells. Minor modifications of pre-treatment and reduction procedures are also described.
Tyrosinase Activity in the Pigmented Cells of the Nucleus Substantiae Nigrae: II. Further Observations on Monophenolase Activity
Authors: Marsden C. D.
Published: April 2021

In a previous investigation of tyrosinase activity in the cells of the nucleus substantiae nigrae of adult cats and monkeys, diphenolase, but not monophenolase activity, was detected. This is possibly due to inhibition of monophenolase. When the copper radicle in tyrosinase is oxidized, monophenolase cannot be detected, but reducing agents activate and unmask this component of tyrosinase.

The effects of reducing agents in activating monophenolase have been investigated. Tyrosine is converted to melanin by monophenolase in adult nigra cells of the cat and monkey when the enzyme is activated by the reducing agents L-dopa, L-ascorbic acid, and L-adrenaline. Variations in physical factors influence the intensity of the activated monophenolase reaction resulting from incubation of sections in tyrosine-dopa mixtures; the reaction is inhibited by general enzyme inhibitors and specific tyrosinase inhibitors.

The significance of the results in relation to tyrosinase activity in adult nigra cells is discussed.
Secretory Structures associated with the Neurosecretory System of the Immature Scorpion, Heterometrus swammerdami
Authors: Habibulla Mohammad
Published: April 2021

Certain previously unknown structures, probably endocrine in nature, are described. The blind ‘end-organ’ which is present and shows signs of activity in the pre-moult stage shows no noticeable sign of activity in the post-moult stage. In certain respects it is comparable to the ‘anterior organ’ of spiders, which has been homologized with the prothoracic glands of insects.

In the rostral region of the scorpion, where the rostral nerve ramifies, an accumulation of leucocytes is found; these show signs of secretory activity. Both at the origin of the rostral nerve and also where it ramifies, neurosecretory material is seen. This rostral structure is comparable in certain aspects with the rostral organ of spiders. Leucocytes occur not only in the rostral organ but also in association with the ‘endorgan’.

The presence of two ganglionic masses, above and below the stomodaeal commissure, suggests the possibility of the sympathetic (stomatogastric) ganglion of the scorpion being a composite structure consisting of the frontal ganglion, the corpus cardiacum, and possibly the hypocerebral ganglion. A hypocerebral ganglion is absent in the adult.
On the Identity of the ‘Neurofibrils’, ‘Nissl complex’, ‘Golgi Apparatus’, and ‘Trophospongium’ in the Neurones of Vertebrates
Authors: David G. B. , Brown A. W. , Mallion K. B.
Published: April 2021

Classical histological methods demonstrate 4 cytoplasmic networks in fixed vertebrate neurones: ‘neurofibrils’, ‘Nissl complex’, ‘Golgi apparatus’, and ‘trophospongium’. The work described in this paper was undertaken to find out whether the 4 networks of classical histology correspond to 4 structures recognizable as such in the living neurone, or to only one structure, which may be coloured in characteristic ways by the classical methods. A single continuous network, comprising features traditionally associated with the four classical networks of the fixed cell, can be isolated by micro-dissection and detected by interference microscopy in living vertebrate neurones. When living neurones are centrifuged at a moderate angular velocity, a single continuous network remains visible under the interference microscope. There does not appear to be enough clear space left for 3 other voluminous structures. When living neurones are centrifuged at a high angular velocity, a single continuous network is pushed to the centrifugal pole of the cell. The remainder of the cell then contains only small separate objects. A single continuous network can be detected by interference microscopy in the cytoplasm of fixed, unstained neurones. When the same cells are dyed by a Nissl method, the cytoplasmic network seen in the unstained cells becomes deeply coloured. When the same cells are bleached and then silvered by a Golgi method, the objects that before had bound the dye now are blackened by the reduced silver. The same effect is obtained when the Nissl method is used after silvering. It is inferred from the results of these experiments that there is only one cytoplasmic network in living normal adult vertebrate neurones. This network is demonstrated in fixed neurones of the same type with varying degrees of faithfulness by the classical methods. It is suggested that the terms ‘neurofibrils’, ‘Nissl complex’, ‘Golgi apparatus’, and ‘trophospongium’ be abandoned.
On the Reproduction of Prionoplus reticularis (Coleoptera, Cerambycidae), with General Remarks on Reproduction in the Cerambycidae
Authors: Edwards John S.
Published: April 2021

Gametogenesis is completed in the pupa in both sexes and the gonads degenerate in the non-feeding adult.

Cyst wall cells, which act as trophocytes, accompany each cyst from an axial germinal region to the radiating follicles. A preliminary account is given of a fibrous structure, the lens of Demokidoff, which overlies the germinal region in the testis lobe.

The morphology of the gut and gonads of the male Ochrocydus huttoni are briefly described.

A distinction is drawn between the reproductive patterns of the subfamilies Pri- oninae and Lamiinae. In the former, where a non-feeding adult is characteristic, gametogenesis is completed in the pupa, after which the gonads degenerate, while in the Lamiinae, where the adult feeds, gamete production continues through adult life. Between these extremes, the Cerambycinae and Aseminae appear to tend toward the prionine condition, and the Lepturinae toward the lamiine.
Properties of the Wall of Leucosolenia variabilis: I. The Skeletal Layer
Authors: Jones W. Clifford
Published: April 2021

Pieces of the wall were photographed while being stretched by a pair of light weights. The extension took place slowly and removal of the weights was not followed by appreciable elastic recoil. On the photographic records, however, slow recoil could be detected in places. The slowness of both extension and recoil are attributed to the mesogloeal matrix and its embedded spicules; the changes in shape necessitated plastic deformation of the matrix.

Changes in the arrangement of the spicules on the photographic records confirm that the matrix underwent plastic deformation, while firmly embedding the spicules. Also the matrix yielded in places, whereupon the epithelia in the vicinity became greatly stretched and recoil occurred on each side of the region concerned.

In some parts of the oscular edge the epithelia contracted and caused the spicules to become crowded together.

Small developing spicules often underwent rotation on the stretching pieces and in some cases the rotation exceeded 180°. While their founder calcoblasts were probably attached to the epithelium which joins the gastral ends of the pores together, the attachment cannot be regarded as permanent, since the rotation, and also spicule growth, require that the calcoblasts at the tips of the rays should be able to move over the surface of the epithelium. The rotation of some developing spicules was associated with a displacement relative to the mesogloeal matrix.

The photographed pieces could not be held for a sufficient time (over 20 h) for new patterns of orientation to be shown by the developing spicules, but on one unphotographed piece this was possible, and small spicules oriented in the opposite direction to the fully formed ones were found near the basal edge, just behind a region of spicule crowding at the edge itself.

The relevance of these observations to the mechanism of spicule orientation is briefly considered.
Properties of the Wall of Leucosolenia variabilis: II. The Choanoderm and the Porocyte Epithelium
Authors: Jones W. Clifford
Published: April 2021

Photographic records of extending pieces of the wall indicate that the choanocytes were but little affected by the stretching process. By adjusting their contacts mutually and by altering their positions on the wall, they avoided becoming greatly stretched in the direction of the applied tension.

Collar-cells cohere together and appear to be under tension in the expanded oscular tube. They also adhere to the inner surface of the wall. There was no evidence of attachment between spicules and choanocytes, and none for a transformation of the latter into pinacocytes, or conversely.

The pattern of pores changed considerably as the pieces extended, pores becoming obliterated and new ones opening up elsewhere. The pores never became slit-like, despite the considerable extension achieved by the pieces. Where pores persisted for a sufficient period, evidence was obtained to support the hypothesis that the porocytes are interconnected to form an epithelium on which the choanocytes can move about and to which, on its other surface, the founder calcoblasts of developing tri- and quadri-radiates are attached.
The egg of Tetrix (Tetrigidae, Orthoptera), with a discussion on the probable significance of the anterior horn
Authors: Hartley J. C.
Published: April 2021

The structure of the egg-wall of Tetrix vittata and the changes that occur in it during development are described. The chorion has a hollow layer held open by struts and freely permeable to both air and water. At the posterior end the struts become finer and the chorion then resembles that of the Acrididae. A thick serosal cuticle develops with a hydropyle at the posterior end. This cuticle is dissolved before hatching. The egg takes up water and increases its volume during development. There is a long horn with a hollow core at the anterior end of the egg. This horn is entirely chorionic and appears to provide the egg with an expansion chamber.
Experiments on fixation for electron microscopy 2. Alkalized osmium tetroxide
Authors: Malhotra S. K.
Published: April 2021

The effect of fixation with osmium tetroxide solution, made alkaline by the addition of potassium acetate, was studied by electron microscopy. Exocrine cells of the pancreas and the cells of the first (‘proximal’) convoluted tubules of the kidney of the mouse were used as test-objects. Partially prepolymerized methacrylate was used for embedding. The preservation of the various cell inclusions was similar to what is generally produced after fixation with Palade’s buffered osmium tetroxide.
The staining of nervous elements by the Bodian method: II. The effects of some variable factors at the impregnation stage
Authors: Williams Terry
Published: April 2021

In paraffin sections of tissues containing much smooth muscle, nerve-fibres are difficult to demonstrate by silver techniques. In pilot trials Bodian’s activated protargol technique proved most promising for stomach sections. From a fixed Bodian-type schedule, the effects of variation in pH, time, and temperature of impregnation were studied separately and together. These experiments provided means of determining optimal levels for some of the variables in the process. The impregnation time required for optimal staining varies according to the temperature and initial pH. Stirring, or agitation of the slides, at intervals of a few hours has been found to be a valuable aid to even staining, and if this has been done it is possible to use the stage of clearing of the fluid as an end-point indicator.
The counting of cells and nuclei in microtome sections
Authors: Marrable A. W.
Published: April 2021

A quantitative relation between the number of nuclei in a tissue and the number of nuclear fragments in its resultant microtome sections has been established by a new method. The general nature of the argument suggested that the correction procedure, although previously restricted to nuclei bounded by membranes, could be applied to mitotic figures and their fragments. With suitable interpretation this was found to be so, and numerical observations are presented which support this extension of the method.

Depending upon their definitions, some of the various mitotic indices in use are theoretically subject to fragmentation error. This effect should be considered and only rejected, as in the example analysed, when it has been proved insignificant.
Changes in the pericardial cells of Periplaneta americana induced by exposure to homogenates of the corpus cardiacum
Authors: Davey K. G.
Published: April 2021

The pericardial cells of the cockroach, Periplaneta americana, undergo change associated with secretion when they are exposed to homogenates of the corpus cardiacum. The cells become markedly larger, and the nuclei send out branches as far as the cell border. Large secretory droplets appear as vacuoles first near the nucleus and later throughout the cytoplasm. Smaller vacuoles come to occupy the area near the periphery of the cell: these are considered to be the remains of the larger vacuoles after they have discharged their contents. Prolonged exposure of the cells to the homogenates in vitro leads to the cessation of these secretory activities, presumably as a result of the exhaustion of metabolites concerned in the secretory process. The cells also become more pronouncedly argentaffin as a result of exposure to the corpus cardiacum. These changes are considered in the light of the discovery that the pericardial cells produce a pharmacologically active material from an inert precursor in response to a secretion from the corpus cardiacum.
The ‘pseudochromosomes’ in the primary spermatocyte of the water-boatman, Notonecta glauca
Authors: Sud Bhupinder N.
Published: April 2021

The ‘pseudochromosomes’ in the primary spermatocyte of the water-boatman, Notonecta glauca, have been studied by phase-contrast microscopy and by the use of vital dyes and histochemical techniques.

They first appear in contact with an inner ‘chromatic’ nuclear membrane, then lie on an outer ‘achromatic’ nuclear membrane, and later they are seen free in the cytoplasm, where they disappear. They differ in their chemical composition from the calottes or juxta-nuclear bodies in the spermatid. They show considerable resemblance in their histochemical reactions with the nuclear ‘spireme’.

It is suggested that they consist of ribonucleoprotein rejected from the nucleus.
The breeding and development of the ascidian Polycarpa tinctor
Authors: Millar R. H.
Published: April 2021

The ascidian Polycarpa tinctor retains its embryos in the peribranchial cavities until they are advanced oozooids. Cleavage is total and leads to a spherical embryo with an outer’layer of ectoderm and a large central mass containing scattered endodermal and mesodermal cells. The gut first appears as a narrow space in the endoderm and differentiates as the embryo elongates. The first stage oozooid has 8 protostigmata and has the branchial and gut cavities filled with a non-cellular substance. This substance is absent in advanced embryos, which have 11 rows of definitive stigmata.
The development of the Malpighian tubules of Carausius morosus (Orthoptera)
Authors: Savage A. A.
Published: April 2021

In Carausius morosus Brunn (Phasmidae) the Malpighian tubules are morphologically and physiologically differentiated into 3 distinct types. The appendices are of unknown function, number about 31, and are inserted separately from one another over the posterior third of the mid-gut. The excretory and calciferous tubules are arranged in groups at the extreme posterior end of the mid-gut. There are 20 to 27 groups each consisting of one excretory and 5 calciferous tubules opening into a small ampulla.

The tubules arise in 5, occasionally 6, generations; 2 in the embryo and one in the second, third, fourth, and sometimes in the fifth nymphal instars. The first embryonal generation is composed of the 24 to 37 appendices (pre-moult embryonal tubules), the second of the 20 to 27 excretory (post-moult embryonal) tubules. The number of calciferous (nymphal) tubules produced in each generation depends largely on the number of groups; there are usually 2 per group in the second and third instars and one in the fourth. Occasionally a single tubule is added to some groups in the fifth instar. The appendices pass backwards and are attached to the anterior parts of the hind-gut; the excretories first pass forwards, then backwards and are attached to the hind-gut just anterior to the rectum, whilst the calciferous tubules are attached distally to the fat-body.

Each tubule is composed of 5 rows of spirally arranged cells which appear as hexagons in surface view. The excretory tubules are differentiated into upper and lower segments and are attached to the gut by a series of short tracheae. The calciferous tubules have a distal region filled with a white crystalline substance and are served by single spiral tracheae. The appendices are not differentiated into segments and have no tracheal supply.

The development of any one tubule comprises a period of initiation and elongation by cell-division, and a period of differentiation. The first period is restricted to the first few days of a stadium, i.e. is linked to cyclical development, whilst the second continues through the remainder of the life of the insect.

The secondary tubules of any one group are added alternately on either side of the first formed tubule along the line of the posterior interstitial ring, and the arrangement of tubules is a result of curvature of this ring.

Tubule buds formed in a particular instar may complete their phase of cell-division in that instar or may remain dormant until the similar period in the succeeding instar.

The calciferous tubules undergo a rudimentary metamorphosis in the sixth (last) nymphal stage.
The effect of light and darkness on the fine structure of the retinal clubs of Dendrocoelum lacteum
Authors: Röhlich P. , Török L. J.
Published: April 2021

The number and size of the vacuoles in the retinal clubs of the eye of Dendrocoelum lacteum increase considerably in animals kept in darkness. As a consequence, the volume of the whole retinal club enlarges, the microvilli forming its marginal zone becoming shorter and thicker. When exposed to light, the retinal clubs regain their original structure; the number and size of the vacuoles diminish and the zone of the microvilli widens. These structural changes are interpreted as due to a photosensitive substance which is produced in the axial cytoplasm of the club, stored in vacuoles and disintegrated by light in the zone of the microvilli.
A cytological and cytochemical study of the ‘epithelial body’ on the carotid artery of the lizards, Trachysaurus rugosus and Tiliqua occipitalis
Authors: Rogers D. C.
Published: April 2021

Epithelial body III of Tiliqua occipitalis and Trachysaurus rugosus has been the subject of a histological and cytochemical investigation with the object of making a comparison with the mammalian parathyroid gland. The cytochemical reactions of the reptilian chief cell are similar to those of the mammalian ‘pale principal’ cell. On the basis of a series of cytological and cytochemical changes a secretory cycle commencing with the chief cell and culminating in the water-clear cell is postulated. Two further cell types distinguished as the dark cell and the ‘epithelial’ cell have been described in the reptilian epithelial body. The significance of these two cell types is discussed. There is some evidence suggesting that true sinusoids invest the cellular cords. There is no evidence, with the technique used, that the gland cells are innervated. It is suggested that the general histology is comparable to that of the mammalian parathyroid gland.
The dorsal nerves of cyclorrhaphan larvae: giant cells in which secretory channels appear at the onset of puparium formation
Authors: whitten Joan M.
Published: April 2021

Median dorsal nerves have been recorded in many Diptera Cyclorrhapha, but their histology has never been considered. It is shown here that they are very different histologically from the lateral segmental nerves. They are invested in a limiting membrane, have no nuclei other than a single large nucleus for each nerve, and the cytoplasm is homogeneous in appearance. These so-called ‘nerves’ are here considered to be giant cells. At the onset of puparium formation, granules appear in the cytoplasm, and this is followed by the establishment of interconnecting channels, disposed peripherally; changes are at the same time observable in the nuclei. The nerves are unbranched until the respective segment is reached; the distal ends of the nerves then give off fine nerve-terminals. The channels within the nerves are seen to converge and pass out into the terminals. These observations suggest that the ‘dorsal nerves’ are giant cells, their nuclei lying not within, but outside the central nervous system, showing considerable similarity to the secretory neurones and secretory nerves associated with the pericardial organs of Crustacea. The nerve-terminals pass to the segmental muscles and possibly play some part in tissue histolysis in the early pupa.
A mechanical drive for the Huxley ultramicrotome
Authors: Dunn A. E. G.
Published: April 2021

An automatic drive is described which ensures a constant cutting rate, and makes easier the cutting of uniform serial sections.
The histophysiology of the saccus vasculosus of Notopterus chitala (Teleostei)
Authors: Sundararaj Bangalore I. , Prasad M. R. N.
Published: April 2021

The apical protrusions of the coronet cells of the saccus vasculosus in Notopterus chitala contain glycogen which passes through the hairs into the globules. In spite of the availability of normal blood-glucose levels in fed controls, only a few cells in the loculi show glycogen ; thus there are individual differences in the physiological activity of the cells. Specific variations in the distribution of glycogen in the different parts of the coronet cells were observed under conditions of starvation and glucose adminis- tration. Starvation for 48 h resulted in depletion of glycogen unidirectionally from the apical protrusion towards the globules. Fish starved for 46, 44, and 42 h were injected intraperitoneally 20% glucose (2 g of glucose per kg of body-weight) and autopsied 2, 4, and 6 h respectively after glucose administration. Comparison of the results obtained with starved fish injected with glucose suggests the gradual conver- sion of blood-glucose into glycogen. This conversion appears to begin at the base of the cell-body and to move towards the apical protrusion. The saccus vasculosus in Notopterus chitala is possibly a source of glucose for the cerebrospinal fluid.
Intracellular sites of activity in the histogenesis of tunicate vanadocytes
Authors: Kalk Margaret
Published: April 2021

The stages in the formation of haemovanadin in fibroblasts of Ascidia pygmaea Michaelson have been investigated with an electron-microscope. The histochemical and vital studies of Endean (1960) on the blood-cells of Phallusia mammillata and the chemical analyses of haemovanadin by Bayer, Bielig, Califano, and Wirth (1954) have been used as a guide to the interpretation of the structures observed.

Pinocytosis of the pharyngeal and intestinal epithelia occurs, during which vanadium, probably bound to acid mucus, is absorbed into the blood-spaces. Amoebocytes pick up vesicles of mucus which are then dissolved in vacuoles. Vanadium is seen to accu- mulate on the vacuolar membranes as the contents of the vacuoles are concentrated and chelated with sulphate and protein. The complex formed is considered to be a precursor of the haemovanadin molecule and can be used as a marker in later stages of histogenesis. When first formed on the vacuolar membrane the vanadium-complex particles are about 3 mμ in diameter. When they are precipitated into the large vacuole formed later by fusion of small ones, the granules are compound and measure from 60 to 100 mμ.

Collection and concentration appear to cease when the amoebocyte turns into a ‘signet-ring’ cell, with a single large storage vacuole compressing the cytoplasm and nucleus into a polar cap. At this stage the synthesis of haemovanadin begins in the cytoplasm as oval grains of protein, 150 by 300 mμ, contained in vacuoles formed at the vesicular ends of Golgi bodies and surrounded by ribosomes. The grains of protein are then surrounded by vanadium-complex material which has been removed from the large vacuole by a process similar to the ‘ropheocytosis’ of ferritin in erythroblasts. The new vanadium-protein compound is distributed in vacuoles around the periphery of the cell, and finally the contents become acid and active haemovanadin proper is formed. The cell is now a ‘compartment cell’.

The vacuoles increase in size, owing probably to their absorption of sugars in the blood near the gut, and they become turXgid with fluid so that the cell resembles a morula. In the early vanadocyte extremely electron-dense particles are visible on the vacuolar membrane, about 20 mμ in diameter. It is probable that they are particles of haemovanadin. In the older vanadocyte the turgid vacuoles become filled with grains of cellulose-like polysaccharide, 30 to 50 mμ in diameter. The test of the tunicate shows amoeboid vanadocytes with long pseudopodia, from which polysaccharide fragments are deposited in the matrix.

It is concluded that the formation of haemovanadin in several separate stages is the result of the activity of vacuoles whose membranes change their specialized enzymic and permeability properties, while the vacuoles retain their identity.
Microvilli on the external surfaces of gastropod tentacles and body-walls
Authors: Lane Nancy J.
Published: April 2021

In Helix aspersa the ‘cuticle’ on the free surface of the external epithelial cells of the optic tentacles has been shown to consist of a layer of microvilli. Microvilli are also present in the same species on the free cell borders of the body-wall, and in the slug Arion hortensis, on the outer cell surfaces of the external epithelium.

In all three cases the microvilli are arranged in a hexagonal pattern. There are indications that branching may possibly occur. The microvilli have granular cores with cross- and longitudinal-striations and there are fibrillar connexions between their tips. On the tentacular and body surfaces of H. aspersa, the microvilli increase the surface area 15 and 12 times, respectively. On A. hortensis the increase in surface area is only 4 times.

In H. aspersa, beneath the microvilli on the tips of the optic tentacles there is a layer, about 3 to 4 μ deep, composed of vertical, horizontal, and tangential fibres. Some of these fibres are attached to lamellar bodies, which may have a lipid content. Granules are also found among the fibres. Further, a greater depth of cuticle is found to be present on the tips of the inferior tentacles of H. aspersa than on their sides ; this seems to indicate that a fibrillar layer, similar to that on the optic tentacles, may lie beneath the cuticle of microvilli on the tips of the inferior tentacles. A thicker cuticle is also found on the tips of the optic tentacles in other stylommatophoran pulmonates. It has not been found possible to ascertain whether the fibrillar layer is intracellular or extracellular, although the evidence points to the latter.

Histochemical tests indicate that mucopolysaccharide is present on the surface of the cuticle. Electron micrographs show a granular precipitate caught on and between the fibrillae connecting the tips of the microvilli. It is suggested that the function of the microvilli is to hold the mucous secretions on the body-surface, which would give protection to the animals.
Muscle fibres and efferent nerves in a crustacean receptor muscle
Authors: Cohen Melvin J.
Published: April 2021

The accessory flexor muscle of the crab myochordotonal organ consists of two kinds of muscle-fibres. In one type the fibrillar material has a uniform punctate appearance in cross-section. The Z bands are often broken across the fibre width and are spaced 2 to 3μapart. These resemble the ‘Fibrillenstruktur’ muscle of vertebrates. In the second fibre type the fibrillar material appears as large clumps in cross-section and it is often difficult to distinguish the outlines of individual fibres. The sarcomere length is 10 to 12μ. These resemble the ‘Felderstruktur’ muscle of vertebrates.

Two types of expanded structures are seen in conjunction with the two efferent neurones innervating this muscle. With fresh material under phase microscopy one type appears as a 20 by 40μrectangular plaque containing vacuoles as well as dark clumps and granules. The other kind of enlargement consists of a group of spheres giving the appearance of a grape cluster and measuring 40 μin its greatest dimension. It is suggested that these expanded structures may be associated with efferent nerve terminations in this muscle.
The photographic development of coloured grains in radioautographs
Authors: Sims R. T. , Graham C. A.
Published: April 2021

Tissue sections are prepared and coated with NTB 3 Eastman Kodak emulsion for radioautography in the usual way. After they have been exposed for a suitable time they are processed with no agitation in the following solutions, which must be freshly prepared. Place for 3 min at 24° C in a developer solution which contains per litre 40 g sodium carbonate, 2 g sodium sulphite, 1 g potassium bromide, 2·5 g ‘genochrome’, 40 ml ethylene glycol, and 100 ml acetone in which 2 g of α-naphthol is dissolved. Wash for 2 min in running tap-water. Place for 2 min in a solution containing 30 g potassium ferricyanide and 15 g potassium bromide per litre. Wash for 2 min in running tap-water. Place for 2 min in a solution containing 40 g sodium sulphite, 240 g sodium thiosulphate, and 100 ml commercial formalin per litre. Wash in running tap-water for 2 min. Place in 0· 02% neutral red for 5 min. Wash in distilled water for 1 min. Dip in a solution containing 10 g gelatin and 1 g chromealum per litre, which has been heated in a water-bath until liquid, and then allowed to cool to room temperature. Stand each slide vertically to dry in air, then mount a coverslip with Canada balsam. This method gives blue grains : if red ones are required substitute p-nitrophenylacetonitrile (Eastman Kodak) for α-naphthol.
Further uses and methods of processing of fresh frozen sections of peripheral nerve
Authors: Williams P. L. , Wendell-Smith C. P. , Finch A. , Stevens G.
Published: April 2021

Advantageous modifications of a fresh frozen sectioning technique for peripheral nerve (Williams, 1959) include reduction in size of the block of supporting tissue, the use of human hair as a ligature, the multiple embedding of specimens and the use of liver sandwiches for irregular specimens. Observation with oblique incident illumination indicates that fresh sectioned fibres remain approximately cylindrical. Fresh sections treated for 5 min with common fixatives such as 10% formal saline, Bouin’s fluid, and Flemming’s fluid show widespread changes in the outline, texture, and dimensions of the myelin sheaths. A modified Flemming fixation/haematoxylin staining method may be used with fresh sections; this gives reasonable preservation of the external sheath boundary but is unsuitable for measurements of internal diameter. Luft’s buffered potassium permanganate solution provides an easily standardized, effective method of producing permanent preparations for quantitative studies. Holmes’s silver impregnation technique may be adapted for use with fresh frozen sections. Interferometric estimations may be made upon axoplasm using 5 μ fresh frozen sections in saline. Care must be taken to determine the axoplasmic thickness present. Adequate sampling of an extended section, when using shearing system objectives, may be accomplished by serial stripping of the section under the dissecting microscope.
Ultrastructural differentiation of the basement membrane of the mouse seminiferous tubule
Authors: Baillie A. H.
Published: April 2021

The development of the basement membrane of the mouse seminiferous tubule has been studied between birth and the end of the tenth week of postnatal life by means of the electron microscope. The sheath cells which surround the seminiferous tubules are derived from mesenchymal cells, and differentiation of these specialized cells continues for 5 weeks after birth. Between the plasma membranes of the sheath cells and those of the Sertoli cells there are 3 distinct zones. The zone of decreased electron density nearest the seminiferous tubule is thought to be specialized extracellular fluid filtered by the second or intermediate zone, which consists of numerous fine particles, and the term ‘pseudomembrane’ is advanced for this zone. Collagen develops in the broad outer zone next to the sheath cells and fulfils the support requirements of the growing tubule.
Further information concerning the envelopes surrounding dipteran eggs
Authors: King R. C.
Published: April 2021

A centripetal migration of follicle cells, which results in a separation of egg and nurse chambers, occurs in higher dipterans like Drosophila melanogaster but not in lower dipterans like Anopheles maculipennis. In Anopheles and Drosophila, while the vitelline membrane can be secreted in the absence of the oocyte, the follicle cells must be present. This suggests that the follicle cell is the governing agent in the synthesis of the vitelline membrane. The envelopes of Drosophila embryos differ from those surrounding ovarian eggs in that a membrane about 0 · 04 μ thick lies directly outside the vitelline membrane. This thin layer is thought to represent a waterproofing wax which forms once the egg leaves the ovariole.
Spittle-production and tube-building by cercopoid nymphs (Homoptera). I. The cytology of the Malpighian tubules of spittle-bug nymphs
Authors: Marshall A. T.
Published: April 2021

Use of the basic dyes toluidine blue and alcian blue reveals stacked circular granules, 1 to 3 μ in diameter, and a highly vacuolated material within the cells of the proximal segments of the nymphal Malpighian tubules.

It is suggested that cyclical secretory activity occurs, involving coalescence of the granules and vacuolation, to produce a secretion which is liberated into the tubule lumen and then passes into the hindgut.