bluuebunny/crossref_metadata_2025 huggingface dataset:
The Structure of the Spermatozoa in Dextral and Sinistral Races of Limnaea peregra
Authors: Selman G. G. , Waddington C. H.
Published: April 2021

Spermatozoa from dextrally and sinistrally coiled races of Limnaea peregra were examined by the use of an electron microscope. Helical fibres in the middle and tailpieces of the sperm were found to be dextrally coiled in preparations from individuals of both races. It is concluded that the genes which determine the direction of spiral cleavage in Limnaea do not control coiling in the sperm.

The structural features of the sperm are discussed in the light of limitations imposed by geometrical considerations on the form of the helical fibres.
Intracellular Membranes
Authors: Young J. Z.
Published: April 2021

Spheres that stain with neutral red in cephalopod neurons show changes with variations in the tonicity of the surrounding medium. In hypertonic solutions the surface becomes shrunken and the stainable matter restricted to crescents or granules at the side of the sphere. These processes are reversible. They may be interpreted by considering that the surface of the spheres consists of material with properties partly analogous to those of a semi-permeable layer and partly to a membrane, that is to say a layer with tangential cohesive forces. These analogies are not perfect, however, and in particular the cohesive properties of the ‘membrane’ are limited and its material tends to flow together to form drops when the inner pressure is reduced.

The appearances produced by the classical methods for staining the Golgi apparatus are a result of distortions of these droplets similar to those produced by changes in tonicity. The outer more osmiophil or argentophil component adopts forms reminiscent of those shown by the component that stains more deeply with neutral red.
On the Origin of the Metazoa
Authors: Hardy A. C.
Published: April 2021

A new view is expressed regarding the possible evolution of the Metazoa from unspecialized and relatively simple Metaphyta, instead of from colonial or partitioned Protozoa.
On the role of the integument in acarine development and its bearing on pupa-formation
Authors: Jones Bryn M.
Published: April 2021

Typical development in mites begins with the retraction of the epidermis from the cuticle. It is accompanied by a decrease in size and a change in shape. Atypical development also begins with a moult. But it is distinguished by regrowth, a change in shape, and an extra moult.

Each moult is unique in that the epidermis divides into an outer and an inner layer. The outer layer adheres to the old cuticle. Its cells are provisionally regarded as being the source of the moulting enzymes. The inner layer retracts and persists as the true epidermis.

The components of mite cuticle, according to histochemical tests, resemble those of insect cuticle.

The formation of a provisional cuticle during atypical development produces the condition generally recognized as a pupal state. The moult of this provisional cuticle is primarily aimed towards synchronizing cuticle deposition with muscle development. Integration of the intermediary connecting processes, the fibrillae, with both the muscle ends and the cuticle is thus made possible.
The Thoracic Glands of Hemiptera Heteroptera
Authors: Wells M. J.
Published: April 2021

The thoracic glands of the pyrrhocorid Dysdercus cingulatus are described. They originate in the second maxillary segment and grow backwards with the salivary gland system. During post-embryonic development the gland nuclei increase in size but not in numbers. In each instar they enlarge, discharge their secretion, and shrink. The thoracic glands of ten other Heteroptera from eight families are described. All consist of large granular nuclei with little surrounding cytoplasm, most commonly arranged as a pair of elongated ductless glands lying parallel to the salivary ducts and attached distally to either the principal or the accessory glands. The thoracic glands are well supplied with tracheoles, but unlike other insects in which corresponding organs have been described, do not appear to have a nerve supply. The number of nuclei in each gland is surprisingly constant, being about 300 in almost all the species examined, the volume of the gland being greater in the larger insects by increase in the size of individual nuclei. The glands disappear very rapidly after the last moult.
The Optical Measurement of Depth
Authors: Galbraith W.
Published: April 2021

The formula for vertical measurement by means of the fine adjustment of the microscope, n2/n1 × measured depth = real depth, is true, where n2 is the refractive index of the object and n, is that of the immersion medium of the objective lens. The refractive index of the mountant is unimportant.

Several additional complications of this method of measurement suggest that it should not be used unless it cannot be avoided, or rough figures are required quickly.
A Study of the Argentaffin (Kultschitzky) Cells in frozen-dried Tissue by Phase-Contrast Microscopy and Ultra-Violet Light
Authors: Christie A. C.
Published: April 2021

The argentaffin cells in guinea-pig intestine have been studied by phase-contrast microscopy and in ultra-violet light. Frozen-dried tissue has been used. One such cell in a section 5–7μ thick was selected and studied throughout. In an unfixed section mounted in nonane, the cytoplasm is packed with fine granules which emit a greenish-yellow fluorescence in ultra-violet light of wavelength 2,750 Å. There is also photographic evidence of absorption of light of this wavelength. After formaldehyde fixation the fluorescence changes to orange-yellow and becomes much weaker. The absorption of light by the granular cytoplasmic contents is also greatly reduced. There is no fluorescence and no photographic evidence of absorption of light of wavelength 2570 A by the granular cytoplasmic contents, either before or after formaldehyde fixation. The nuclear chromatin pattern in these cells is unaltered by formaldehyde fixation, and is well demonstrated in photographs taken in ultra-violet light of both the wavelengths mentioned above.
The Sheath of Spicules of Leucosolenia complicata
Authors: Jones Walter Clifford
Published: April 2021

Dilute hydrochloric acid, carbonic acid, and potassium nitrate solutions dissolve the spicule calcite revealing a thin, partially contracted sheath. Corrosion by potash solution, however, produces a rigid, brittle ‘sheath’, which consists of the true sheath and an inorganic deposit laid down on its inner surface as the calcite dissolves away.

The oscular rays, gastral rays, and curved monaxons corrode much more rapidly than the basal rays and slender monaxons in potash solution, and the corrosion is most noticeable on the surfaces transverse to the optic axis, particularly when dilute potash is used. Potassium nitrate solution and water, however, corrode the surfaces parallel to the optic axis, whereas in hydrochloric and carbonic acid solutions the calcite dissolves uniformly all round the rays.

When spicules bearing calcite crystals are corroded, the calcite of the spicules dissolves more rapidly than the crystals, which then remain attached to the sheath and appear to have crystallized upon it, though attempts to crystallize calcite upon isolated sheaths, or sheaths supported by the inorganic deposit, have been unsuccessful. The evidence suggests that when crystals form on the spicule surface they are oriented by crystallizing on the calcite through perforations in the sheath.
The Cell-theory : a Restatement, History, and Critique: Part V. The Multiplication of Nuclei
Authors: Baker John R.
Published: April 2021

The belief that nuclei arose by exogeny, without relation to pre-existent nuclei, was due mostly to Schleiden (1838). Kôlliker (1843) supposed that new nuclei arose by endogeny within pre-existent nuclei.

Other early theories of the origin of nuclei contained a considerable element of truth. Many early workers thought that the ordinary nuclei of many-celled plants and animals multiplied by division (Bagge, 1841 ; Nageli, 1844; von Baer, 1846), or by the disappearance of the old nucleus and its immediate replacement by two new ones (Nageli, 1841 ; Reichert, 1846).

The history of the discovery of mitosis falls into three parts.
Axial Illumination in Microscopy
Authors: Galbraith W.
Published: April 2021

A simple and accurate method of ensuring axial illumination is described. It involves examining a suitable cardboard disk held in the substage filter-holder and checking that the image of the field-stop is central in the field of view.
Observations on the Stomach and Digestive Diverticula of the Lamellibranchia: I. The Anisomyaria and Eulamellibranchia
Authors: Owen G.
Published: April 2021

A study of the digestive diverticula of the Anisomyaria and Eulamellibranchia revealed certain features hitherto undescribed. The diverticula consist of blind-ending tubules which open into ciliated main ducts by way of short, non-ciliated secondary ducts. The main ducts open into the intestinal groove. In all the species examined the ciliated epithelium of the main ducts was restricted to a well-defined groove, the remainder of the lumen being surrounded by a non-ciliated, brush-border epithelium.

Each tubule is surrounded by a system of smooth muscle fibres. Cilia associated with the darkly staining cells of the crypts were demonstrated in sections of the tubules. After feeding with titanium dioxide in suspension, this substance was later found in the large vacuolated cells of the tubules. The particles of titanium dioxide were larger than 0·1.

A continuous circulation is maintained within the main ducts solely as a result of ciliary activity. The exhalant current in the ciliated portion of the main ducts produces an inhalant counterpart current in the non-ciliated portion. It is suggested that fresh fluid is drawn into the tubules as a consequence of the absorptive functions of the large vacuolated cells. Indigestible material accumulates in the large vacuolated cells and is extruded into the main ducts where it is conveyed out of the diverticula by the exhalant ciliary current.

In both the Anisomyaria and Eulamellibranchia the flap-like major typhlosole prevents material entering the mid-gut except by the intestinal groove, and isolates the rejectory currents of the intestinal groove from the general circulation of particles in the stomach. In the Eulamellibranchia the major typhlosole also acts as a valve which controls the entry and exit of material into and out of the inhalant and exhalant portions of the main ducts.
A Pigment in the Rat’s Uterus
Authors: Warbrick J. G.
Published: April 2021

A yellowish-brown pigment was found at the old placental sites in rats killed at 10 and 20 days after littering. The pigment contained ferric iron and therefore may be regarded as haemosiderin. Other properties of the pigment suggest that there is also a lipid component present. Lipid is not usually associated with haemosiderin. The lipid component behaves in many ways like the lipogenic pigments.
The Site of Damage in Amoebae exposed to Low Concentrations of Methyl di-(β-Chloroethyl)-Amine (a ‘Nitrogen Mustard’)
Authors: Ord M. J.
Published: April 2021

Amoeba proteus was exposed to a low concentration of methyl di-(β-chloroethyl) amine (MBA, a ‘nitrogen mustard’). Subsequent nuclear transfer was used to study the relative sensitivities of nucleus and cytoplasm to MBA. Nuclei were found to be 10 times as sensitive as cytoplasm. Exposure to MBA caused a short delay before the first division of the nucleus and a longer delay before the second division, the delay before the first division being more marked with exposure to LD100 or higher concentrations. The first cytoplasmic division was delayed after treatment but subsequent division showed little change. MBA caused many abnormalities in division. When cytoplasm was injured the nuclei became swollen or, with less severe damage, divided without subsequent cytoplasmic division. When only nuclear damage was present, such abnormalities as incomplete prophase, non-nucleate division, uneven division, and cytoplasmic fragmentation occurred.
Neurosecretory Cells of the Central Nervous System of the Crab, Paratelphusa hydrodromous
Authors: Parameswaran R.
Published: April 2021

Three types of neurosecretory cells, designated A, B, and C, occur in the central nervous system of Paratelphusa hydrodromous. They are distinguishable by their sizes, the nature of their nuclei, and the secretory products in the cytoplasm. Their distribution and neurosecretory activity are recorded in this paper. All the three types occur in the thoracic ganglion, while the brain and tritocerebral connective ganglia contain only the A and B types. Examined alive under the phase-contrast microscope, the conspicuous A-cells reveal the presence of numerous tiny granules and dark spheroids in the cytoplasm. These spheroids are stainable by neutral red. In Golgi preparations the spheroid walls become black. These are sudanophil and probably represent lipochondria. The spheroids contain phospholipid and vitamin C. The granules of the cytoplasm probably represent the mitochondria.

The brain and thoracic ganglia contain within them a rich network of delicate capillaries which surround individual neurosecretory cells as well as groups of cells. The secretory products are possibly discharged directly into the blood.
A Histochemical Basis for Changes in Renal Tubular Function in Young Mice
Authors: Longley James B. , Fisher Edwin R.
Published: April 2021

In the kidney of the adult mouse the tubular epithelium in the most proximal (P1) segment, corresponding roughly to the convoluted portion of the proximal tubule, shows strong alkaline phosphatase activity, and the brush border is moderately reactive to the periodic acid Schiff (PAS) method. In the more distal (P2) segment of the proximal tubule there is no alkaline phosphatase activity, and the PAS reaction of the brush border is intense. Examination of a large number of young mice has now revealed a distinct pattern in the development of this adult condition.

Differentiation of the two segments on the basis of the PAS reaction of the brush border becomes apparent on about the 15th post-natal day. The effect is the result of a decrease in the reactivity of the Pi segment. Differentiation of the two segments on the basis of alkaline phosphatase activity develops gradually between about the 22nd and 36th post-natal days. During this period the alkaline phosphatase activity disappears progressively from the proximal to the distal end of the P2 segment.

The administration of testosterone or estradiol to either sex accelerates the differentiation with respect to alkaline phosphatase activity. Castration of male mice retards the completion of this process.

It is suggested that morphological changes of this type may provide the basis for some of the functional differences between the kidneys of young and mature animals.
Distribution of Iron in Daphnia in Relation to Haemoglobin Synthesis and Breakdown
Authors: Smaridge M. Wendy
Published: April 2021

Daphnia synthesizes haemoglobin in poorly aerated water and loses it in well-aerated water. A histochemical study has been made of iron in the tissues of partheno-genetic female D. magnawhen gaining or losing haemoglobin, and with a steady content of the respiratory pigment.

In animals gaining haemoglobin, loosely-bound iron was found especially in the gutwall, fat-cells, and ovaries. The iron in the gut-wall was probably being absorbed into the body, and that in fat-cells and ovary being incorporated into newly synthesized haemoglobin.

In animals losing haemoglobin, loosely-bound iron was found especially in the walls of the gut caeca, in the fat-cells, and in the excretory shell-glands. Several lines of evidence indicate that iron was being excreted by the shell-glands. It was probably also being excreted through the gut caeca. In the fat-cells haemoglobin can accumulate during haemoglobin loss and it is probably broken down here with the deposition of iron. This iron is subsequently excreted.
Colloidal Properties of the Mesogloea in Species of Leucosolenia
Authors: Jones Walter Clifford
Published: April 2021

Oscular tubes rapidly collapse and disperse in isotonic potassium nitrate solution, the cells dissociating and rounding off, and the mesogloea softening and swelling. Reasons are given for regarding the action as a direct one on the mesogloea and intercellular ‘cement’.

Transference of the collapsing tubes to sea-water, or isotonic calcium chloride, results in an immediate stiffening of the mesogloea, and the swollen cells form characteristic processes which are best seen after the cells have been in the nitrate solution for an optimum period depending on the temperature. They are not formed after treatment with M/1oo potassium cyanide.

The action of other isotonic salt solutions is briefly described. When a comparison is made of the times taken for the tubes to become plastic, the ions respectively used fall into three series which are the same as those found in regard to the dispersiveness of certain hydrophilic organic colloids.

The experiments provide evidence that the mesogloea is secreted by the choanocytes or by the amoebocytes close beneath them, and that the secretion stiffens into a firmer gel as it passes into the spicule zone. The degree of firmness also varies apparently according to the health of the tube.

The action of distilled water and acidified sea-water are described. After the spicules have dissolved the tube still retains its shape and much of its support can thus derive from the mesogloea. The relative functions of the mesogloea and the spicules are briefly discussed.
An Integration Method for the Interference Microscope
Authors: Mitchison J. M. , Passano L. M. , Smith F. H.
Published: April 2021

A method is described of measuring the integrated phase retardation of an object with a Baker interference microscope. With certain limitations, the total dry mass of the object can be derived from this figure. This method of ‘weighing’ objects is of particular value in measuring the growth of single cells, since it is very sensitive and can be used on a living cell without damaging it.

The method consists of restricting the field round the object with an aperture of known area and then measuring the total retardation within this field due to the presence of the object. The compensator is adjusted until there is an equal light intensity in the field with and without the presence of a quarter-wave plate. A similar adjustment is made with the object moved out of the field. The difference between the two compensator settings gives the integrated area retardation due to the object. The quarter-wave plate is motor-driven, and the light intensity is measured by a photomultiplier and presented on a cathode ray tube. The instrument is sensitive to a change of about 5 × 10_ 14 g in the dry weight of a biological object.

For an object of known specific refractive increment and mounted in water, the total dry mass can be derived from the retardation without the dimensions of the object being known. There is, however, a severe limitation with this method of integration— that the maximum retardation of the object must not exceed about 45 º or λ/8. This can be shown by theory, and has also been confirmed by model experiments with small celloidin spheres. Most biological objects have larger retardations in water, so it is necessary to mount them in media of higher refractive index. In this case, the volume of the object must also be known for the dry mass calculation. Although this limits the use of the method, it is important in measuring the growth of a cell to know the volume as well as the dry mass.

An example is shown of the application of this method in measuring the growth of a fission yeast, Schizosaccharomyces pombe. Curves are given showing the changes in dry mass, volume, and concentration of a single growing and dividing cell of this yeast.
The Structure of the Teeth of some Mammal-like Reptiles
Authors: Poole D. F. G.
Published: April 2021

The principal changes in calcified tissues which have fossilized are the loss of organic material and the conversion of hydroxyapatite into fluorapatite. Since these two minerals are very similar and because, initially, mammalian enamel has a low organic content, its optical properties are hardly affected by fossilization. On the other hand, the loss of optically active collagen results in a modification of the characters of dentine.

The teeth of synapsid reptiles possess dentine similar to that of recent reptiles. Occasionally the dentine contained globuli, but unlike mammalian dentine, there appeared to be no ‘spheritic’ orientation of crystallites within the globuli. Certain dicynodont tusks consisted of dentine only and it is possible that enamel was missing even in the original condition. Other synapsid teeth possessed a thin, well-defined enamel layer made up of incremental lamellae but lacking true prisms. Nevertheless, cylindrical groups of crystallites exist throughout this enamel within which the orientation of the crystallite axes varies regularly. Between crossed nicols of a polarizing microscope this crystallite arrangement gives the enamel a prismatic appearance. However, the enamel is quite homogeneous, for these pseudo-prisms are not physically separated from each other. Furthermore, this regular prismatic appearance and an irregular Säulengliederung, such as occurs in crocodile enamel, may exist in the same tooth. There is, therefore, no evidence that the prismatic enamel characteristic of mammals existed in the pre-mammalian reptiles.
Preservation of Animal Tissues, with a Note on Staining Solutions
Authors: Owen G. , Steedman H. F.
Published: April 2021

Methods are given by which animal material, fixed by any desired method, may be preserved against attack by fungi or bacteria. The reagents employed are glycol monophenyl ethers (‘Phenoxetol’), and esters of p-hydroxybenzoic acid (‘Nipa’ esters). These reagents, dissolved in water, produce colourless and almost odourless solutions, in which a variety of animals have been preserved for many months without showing any traces of deterioration or decomposition.
Mucopolysaccharides and the Calcification of the Scale of the Roach (Leuciscus rutilus)
Authors: Wallin O.
Published: April 2021

The scale of the roach (Leuciscus rutilus L.) was examined for state of calcification, metachromasy, and reaction to the periodic acid / Schiff (PAS) test. Metachromasy and a positive PAS-reaction imply acid mucopolysaccharides in the bony layer. There is a great increase in these reactions and in reactions for bone salts in the transition zone between the uncalcified and calcified part of the bony layer. These reactions imply that the bond between the osseoid and the inorganic fraction of the bony layer is through SO2-and PO4-groupings. The fibrillary plate lacks metachromasy, but shows a positive PAS-reaction. Before calcification a strong orthochromasy points to acid groups in connexion with the collagen. Under the radii there is no orthochromasy, and the PAS-reaction is negative. When calcifying, the fibrillary plate loses its orthochromasy and the mineral matter is deposited as large crystal-complexes. In regenerating scales the reactions are weaker than in normal scales.
The Morphology and Origin of the Golgi Bodies and their Role in the Secretion of the Acrosome in the Spermatogenesis of Pulmonate Gastropods as Determined in the Living Material by Phase-contrast Microscopy
Authors: Nath Vishwa , Gupta Brij L.
Published: April 2021

In this paper are embodied our observations on the morphology, origin, and role of the Golgi bodies in the spermatogenesis of the slug, Anadenus altivagus, and the snail, Euaustenia cassida. Living cells have been studied under the phase-contrast microscope and photomicrographed. In the juxta-nuclear Golgi region in primary spermatocytes the Golgi bodies exist in the form of (1) granules and rods of dark contrast, (2) spheres of pale contrast, and (3) spheroids showing a duplex structure, each consisting of a sphere of pale contrast and an incomplete or complete cortex or sheath of dark contrast. The Golgi spheroids have been shown to arise three times in the course of spermatogenesis from the mitochondrial granules by a process of alignment. The acrosome is formed from a cap of tiny acrosomal granules, which are deposited in front of the spermatid nucleus by the Golgi bodies (acroblasts).
Some Observations upon the Cytology of the Pars Distalis of the Surgically-removed Human Pituitary
Authors: Foster C. L.
Published: April 2021

Human anterior pituitary tissue that had been removed at operation and immediately fixed was examined by a number of cytological and histochemical methods and by phase contrast and electron microscopy, and compared with similar material obtained post mortem. The general histological picture of good post-mortem material (not more than 4 hours post mortem) compared well with the surgically-removed tissue. For the study of silver impregnations of the Golgi substance, however, material removed at operation was found to be greatly superior.

Evidence was obtained showing that the intracellular lipid inclusions seen post mortem were not artifacts resulting from cytolytic changes. There appeared to be no relationship between these lipid bodies and the Golgi material as revealed by the Aoyama method.

No unequivocal dimorphism of the Golgi bodies, correlated with α-and α-celIs, such as has been reported to occur in certain other mammals, was observed.

Phospholipid was present in the granules of a substantial proportion of the α-cells.

It was found that most of the cells which had been designated as β-cells after the application of certain routine staining methods, and most of the Gram-positive cells, reacted positively to the Periodic acid Schiff test: these cells could therefore be regarded as true β-or mucoid cells.

A method for the demonstration in frozen sections of the cell-types, together with the lipid inclusions, is described.
Some Cytological Characteristics of Thyroidal Function in the Endostyle of the Ammocoete Larva
Authors: Barrington E. J. W. , Franchi L. L.
Published: April 2021

An account is given of the distribution of thyroidal function in the epithelium of the endostyle of the ammocoete larva, based on the localization of bound iodine as revealed by autoradiographs ; and the cytological characteristics of the various types of cells are analysed in relation to this. The binding of iodine is shown to be correlated with the production of a PAS-positive ‘thyroidal prosecretion’ which, in fully active cells, tends to become transformed into a more granule-like phase. These thyroidal granules appear to have some degree of permanence and to enlarge by the accumulation of material ; the precise significance of this is not clear, but it might involve the laying-down either of secretory reserves or of the by-products of thyroidal metabolism. The granules differ from the initial phase of the prosecretion in developing a brown pigmentation, a positive ferric-ferricyanide response, and a yellowish fluorescence, together with some affinity for orange G. These properties, together with the PAS-positive response of both phases of the prosecretion, give considerable support to the view that the secretory process involved is homologous with that which produces thyroid colloid in higher forms, although the histochemical reactions concerned are not sufficiently specific to be decisive. Thyroidal function is widely spread in the epithelium, except in the glandular tracts (type 1 cells), but it varies in its degree of expression; the pattern of this, and its relationship to the alimentary activity of the endostyle, can conveniently be described in terms of the embryological concept of ‘gradient fields’. The present results are discussed in relation to the fate of certain regions of the epithelium at metamorphosis.
Some Observations upon the Golgi Elements of the Cells of the Surgically Removed Human Anterior Pituitary
Authors: Foster C. L.
Published: April 2021

1. The lipid inclusions of the cells of the pars distalis of the human pituitary are not restricted to the zone occupied by the Golgi element.

2. No evidence was obtained to suggest that a canalicular system is invariably associated with the Golgi zone. The frequency with which such systems were observed appeared to depend on the mode of fixation and other factors.
A Histochemical Study of the Adipose Cell of the Leech, Glossiphonia complanata
Authors: Bradbury S.
Published: April 2021

The adipose cell of the leech Glossiphonia complanata has been studied both morphologically and histochemically. It is more or less globular in shape, with a diameter of from 10 μto 40μ; the protoplasm is clearly marked off into two zones, the ground cytoplasm around the periphery of the cell, and a denser, basiphil zone (termed the ‘surround’) which encloses the fat drops and the nucleus. Large thread-like mitochondria are scattered throughout the cell ; they are especially numerous in the ‘surround’.

Histochemical tests showed that the ground cytoplasm contained arginine, tyrosine, glycogen, RNA, and inorganic iron; the ‘surround’ has, in addition to these, much phospholipid, some unsaturated lipid, and some acid mucopolysaccharide.

The large fat drops and some other smaller fat droplets found in the ground cytoplasm are chiefly composed of neutral lipid, possibly triglyceride; they also contain some cholesterol or cholesteryl esters and some unsaturated lipid. The lipochondria of the ground cytoplasm and the ‘surround’ differ from these in that although they may contain some or all of the substances found in the large fat drops, their principal constituent is phospholipid. The mitochondria also react positively to the test for phospholipid.

Some granules found in the ‘surround’ and in the ground cytoplasm were shown to contain inorganic iron. The ‘fuchsinophil’ granules of Bobin are almost certainly identical with the lipochondria.

Both the large fat drop and the glycogen are reserve food stores.
The use of the baker interference microscope for the study of optically heterogeneous specimens
Authors: Faust R. C.
Published: April 2021

The refractive index of an optically heterogeneous specimen will generally vary in directions parallel and normal to the microscope axis, but a mean index can be defined such that the optical thickness of the specimen is equal to the product of the mean index and the specimen thickness. If such a specimen is examined under an interference microscope, the fringe displacement will be zero at those parts of the specimen for which the mean index is equal to the index of the immersion liquid. Thus, by gradually changing the index of the liquid relative to that of the specimen, one can determine the manner in which the mean index varies from region to region of the specimen. In the present work these changes in relative index have been effected by varying either the wavelength of the incident light or the temperature of the system.

The Baker two-beam interference microscope has been successfully used for such investigations. Three types of interference pattern have been tried: (i) a single fringe is made to fill the field of view and the intensity differences between the specimen and the background are studied; (ii) monochromatic fringes are formed in a quartz wedge and their linear displacements are examined; and (iii) a quartz plate is used, channelled spectra being produced by the spectrographic analysis of the interference colours. The first two types can be used with either the temperature or the wavelength variation method, but the third was specifically designed for use with the wavelength variation method. Although these experiments have mostly been carried out on birefringent fibres, the techniques are applicable to any kind of object. The attainable accuracy increases with specimen thickness; under favourable circumstances the index at any point of a specimen io µ thick should not be in error by more than ±3 × 10-4.
A Modified Ester Wax for Embedding Tissues
Authors: Chesterman W. , Leach E. H.
Published: April 2021

1. A modification of Steedman’s ester wax embedding method is described. This involved purification of two of the components—diethylene glycol monostearate and distearate. The puckering and floating off of the sections is thereby minimized.

2. The method is particularly applicable to tissues containing much collagen and to tissues that have been badly fixed or which have undergone post-mortem degeneration.

3. Cytological preservation is improved, especially that of such substances as glycoproteins and mucoproteins.
Improvements in the Sudan Black Technique
Authors: Baker John R.
Published: April 2021

The author’s Sudan black technique has been improved by changes in fixation. One may fix as for the acid haematein test, or else in a modified Flemming’s fluid. The former fixation allows very strong colouring by Sudan black, while the latter gives particularly faithful preservation of the form of the cells and their lipid inclusions.
The Male Genital System of the Scorpion, Buthus quinquestriatus
Authors: Abd-El-Wahab A.
Published: April 2021

1. The paper consists of a morphological and histological description of the male genital system of the scorpion, Buthus quinquestriatus (H.E.).

2. There is a well-developed ganglionic mass at the extreme end of the lumen of the cylindrical gland. This ganglionic mass has not been recorded by any of the previous authors.

3. There are two pairs of annex glands opening into the common genital chamber. None of the previous authors have observed such a gland with the exception of Pavlovsky (1915), who recorded it in B. australis.

4. New methods have been adopted to resolve the structure of the ejaculatory organ and its supporting shaft. The organs were cut in serial transverse sections, and whole mounts were also made.

5. In the supporting shaft, several basal processes have been found, namely, the oblique vertical, longitudinal, superior, and inferior outer and inner processes.

6. The supporting shaft is found to be of a chitinous nature.
Seasonal Lipid Changes in the Sexual Elements of a Male Snake, Vipera berus
Authors: Marshall A. J. , Woolf F. M.
Published: April 2021

In the seminiferous tubules and interstitium of the viper there occur cyclical changes basically similar to those in birds and the pike. These involve the metamorphosis of unshed germinal material into cholesterol-positive lipids, the rehabilitation of the interstitium after the seasonal depletion of its cytoplasmic lipids and cholesterol shortly after the spring emergence from hibernation, and the completion of spermatogenesis after basking in the sun. The viper differs from birds in that its tubule lipids contain much less cholesterol; also, the subsequent spermatogenesis begins almost immediately (as in poikilothermous pike and frog), and proceeds to the spermatid stage in the presence of such lipids. Further, although in some individuals new Leydig cells rapidly mature, this resurgence is delayed in others. Thus, although the succeeding spermatogenesis always begins in still-lipoidal tubules, it may do so in the presence of a largely non-lipoidal interstitium. Mitoses were observed in mature Leydig cells. Fibroblasts occasionally alter to take on an apparently glandular function.

By July most animals had regained a heavy lipoidal and cholesterol-positive interstitium, lost most of their tubule lipids, and possessed either secondary spermatocytes or, sometimes, spermatids. This internal activity is probably partly responsible for autumnal sexual behaviour. Factors additional to temperature control spermatogenesis, for only a few spermatozoa are formed by the time of hibernation in October. No pronounced retrogressive changes occur during hibernation: the cycle merely halts, and begins without further delay on emergence. Thus spermatogenesis may be at its peak by the end of March.

The expanded, glandular ‘sexual segment’ of the male renal tubule also exhibits cyclical changes involving the production and expenditure of cholesterol-positive lipids, but such changes take place also in narrow parts of the tubule and, further, in the kidney of the female.
The Contractility and Healing Behaviour of Pieces of Leucosolenia complicata
Authors: Jones Walter Clifford
Published: April 2021

The behaviour of isolated pieces of Leucosolenia complicata confirms that this sponge vis contractile. The pieces first curl up owing to a contraction of the internal epithelium, which can exert a tension in one direction (transverse) more than the other at right angles. The contraction is slow because it entails a redistribution of the supporting mesogloea. It is abolished by 5 minutes’ treatment with distilled water.

Healing next involves the formation of ‘healing membranes’. Each membrane consists of two epithelia with a thin layer of mesogloea in between. The membranes arise either as an outfolding of the internal epithelium or from the cut edges of the wall, and they spread between the edges so that the tubular form of the olynthus is regained. Their spread is due to the maintenance of tension in the membrane, coupled with the shrinkage of the remainder of the piece.

Pieces from which the internal epithelium has been brushed away shrink rapidly and become saddle-shaped, indicating that the dermal epithelium also is contractile.

No important differences are noticeable when the healing behaviour takes place in equal parts of sea-water and isotonic magnesium chloride, which suggests that the behaviour is not under the control of a nervous system.

A discussion is given on the elements responsible for the contractility of the internal epithelium. It is probable that the porocytes are connected beneath the bases of the collar-cells, and are the contractile cells concerned.
The Anatomy of the Infra-red Sense Organ in the Facial Pit of Pit Vipers
Authors: Bullock Theodore H. , Fox Wade
Published: April 2021

The histological composition, of the sensory membrane in the facial pit of rattlesnakes (Crotalus spp.), the disposition of the nerve-trunks entering it, the fibre-size spectrum of the nerves, and the form of the sensory endings are described. Between the two layers of extremely attenuated epidermis the principal constituent of the membrane is a single layer of specialized parenchyma cells with osmiophil, reticular cytoplasm. These are not regarded as sense cells but they react strongly and locally to degeneration of nerve-endings. The axons enter through numerous trunks from three branches of the trigeminal nerve, from all sides of the membrane, providing a dense innervation. They lose their myelin, taper to about 1 p, then expand into flattened palmate structures which bear many branched processes terminating freely over an average area of about 1,500 p.2, overlapping only slightly with adjacent units but leaving virtually no area unsupplied. This means there are from 5 00 to 1,5 00 axons ending per mm2, an estimate which agrees with the nerve-counts. No other form of ending was found. The mode of the fibre-size spectrum lies in the region 5-7p diameter. A transmission spectrum of the fresh membrane shows broad absorption peaks at 3 and 6 p and about 50% transmitted in other regions out to 16p. The visible spectrum is at least 50% transmitted and probably much is lost by reflection. Strong absorption takes place at wavelengths shorter than 490 p. The anatomical adaptations of the sense organ are discussed, especially the concentration of warm receptor fibres, the thinness of the membrane, the extremely superficial position of the nerve-endings—all increasing sensitivity to caloric flux. The overhanging margins of the pit and the richness of supply are believed to permit directionality of reception. It is suggested that the palmate form of the ending has a significance in permitting several independent local subthreshold activity generators to coexist in the processes and in pooling their coincident, electrotonically spread potentials to influence the initiation of spikes which may take place at the junction of axon and palm.
Spider Leg-muscles and the Autotomy Mechanism
Authors: Parry D. A.
Published: April 2021

Spider leg-muscles have been redescribed and the absence of extensor muscles at two joints confirmed. The possibility that the flexors at these joints act in antagonism to the blood-pressure is discussed. The coxal muscles are inserted on to sclerites in the rim of the trochanter and autotomy occurs at this joint. At autotomy the sclerites are detached from the trochanter and support the articular membrane, which restricts bleeding.
The Uptake of 38S in Cortical Bone
Authors: Lea Lorna , Vaughan Janet
Published: April 2021

A further study of the uptake of 35S in rabbits and in normal and rachitic puppies has been undertaken. The non-labile 35S present in osteoid tissue is removed by testicular hyaluronidase, but not by staphylococcal hyaluronidase, which suggests that it is chondroitin sulphate A or C. The non-labile 35S is first taken up by noncalcified osteoid tissue in the area giving a pale pink PAS reaction. It is only later found in calcified bone when the tissue ceases to be PAS-positive. Rigid attention to technical detail is essential if comparable results are to be obtained in studies of borte uptake of 35S.
Some Aspects of the Structure and Cytology of the Gills of Lampetra fluviatilis
Authors: Morris R.
Published: April 2021

A description is given of the structure and vascularization of the lampern gill.

A comparison of the cellular components of the gill epithelium taken from lamperns at various stages of their spawning migration show that certain types of cells are common to all animals. These include the cells covering the gill platelets, the mucous cells, and certain basal cells from which others originate. The mucous cells are quite different in structure from those of teleosts.

There is a progressive loss of large acidophilic cells from certain regions of the gill filament as animals enter fresh water during the earlier stages of the spawning migration. These cells are similar in both structure and location to those described as chloride excretory cells from the gills of marine teleosts. They are typically large, flask-shaped cells with basal nuclei and they are filled with rod-shaped or spherical mitochondria. It is believed that they are responsible for the extra-renal excretion of monovalent ions during the process of marine osmoregulation in the lampern. The chloride excretory cells are very numerous in a limited number of fresh-run animals which are able to osmoregulate in 50% sea water.

In the normal course of events the chloride excretory cells are replaced by a smaller type of cell which is also rich in mitochondria, but unlike the excretory cells these lie at the surface of a transitional epithelium. It is argued that these cells may be responsible for ion uptake from fresh water in the maturing animal.

In male lamperns, large glandular cells of unknown function appear in the gill epithelium as the animal nears the time of spawning.
The Coelomocytes of Holothuria leucospilota
Authors: Endean R.
Published: April 2021

Morula-shaped cells, structurally similar to fibre-producing cells occurring in the blood and test of an ascidian, Pyura stolonifera, have been found in the coelomic fluid and Cuvierian tubules of Holothuria leucospilota.

The morula-shaped cells of the holothurian are formed from primitive amoebocytes. They contain globules, each of which consists of a central core of proteinaceous material associated with an unidentified iron compound. A film of polysaccharide materia1, containing granules of a lipo-protein nature, surrounds the core. Part, at least, of the polysaccharide is mucopolysaccharide. It is believed that the materials present in the globules are precursors of collagenous connective tissue fibres.

The mean value of the iron content of the corpuscles was found to be 0·12 g per 100 g dry weight. The iron is organically bound but does not appear to have chemical relationship to haem or other similar iron-porphyrin compounds.

Fibrous processes arise from many morula-shaped cells when they are cytolysed with distilled water.

In hanging-drop preparations some morula-shaped cells eject globules which trail fibres. It is believed that the globules are directly involved in fibre-production.

Granules, similar in many respects to the globules of the morula-shaped cells of the holothurian, have been found in vertebrate fibroblasts.
Activity of the corpora allata during pupal diapause in mimas tiliae (lepidoptera)
Authors: Highnam K.C.
Published: April 2021

Histological observation indicates that the corpora allata of Mimas tiliae are secretory during pupal diapause, but become inactive by the end of the low-temperature period which terminates diapause.

Removal of the corpora allata, together with the corpora cardiaca, from the dia- pausing pupa increases the thickness of the hypodermis and decreases the number of fat-body inclusions (compared with operated controls), but does not result in any visible signs of diapause break.

The oxygen uptake of the pupa increases by about 60% by the end of the low- temperature period, compared with the diapausing pupa.

It is probable that the corpora allata play some part in the maintenance of diapause, possibly by exercising some control over the fat-body metabolism. This role is subservient to that of the neurosecretory cells in the brain, together with their associated corpora cardiaca.
The Fine Structure and Morphological Organization of the Peripheral Nerve-fibres and Trunks of the Cockroach (Periplaneta americana)
Authors: Hess Arthur
Published: April 2021

Sections of the peripheral nerve-trunks of the metathoracic leg of the cockroach (Periplaneta americana) were studied with the electron microscope. Paraffin sections were also prepared and stained. Protargol succeeds in staining the nerve-fibres. Osmium tetroxide, a modified Weigert procedure, and Luxol fast blue stain the myelin sheaths, as does mercuric bromphenol blue, a protein stain. The axoplasm is relatively free of formed elements; it contains mitochondria. The myelin sheath, when present on the largest and also some smaller fibres, consists of about two or three loose over-lapping processes of Schwann cells, covered by their plasma membranes, enclosing lipid-like droplets and having a beaded appearance. Between the nerve-fibres in the nerve-trunk is Schwann-cell cytoplasm, which arises from Schwann cells that sur-round the whole nerve-trunk. The same fold of Schwann-cell membrane may enter into the formation of the myelin sheath around more than one nerve-fibre. Several small non-myelinated fibres, which may be as small as 0 · 3 μ. in diameter or less, may be enclosed in the same fold of Schwann-cell membrane. Outside of the Schwann-cell layer and surrounding the nerve-trunk is a thin layer of connective tissue, which does not send trabeculae into the interior of the nerve. Tracheae and tracheoles accompany the nerve but are not included within the sheaths surrounding a nerve-trunk, even near the termination of the nerve-fibres in muscle. The structure of the cockroach peripheral nerve is compared with that described by previous investigators, with that of other insects, and with invertebrate and vertebrate nerve.