bluuebunny/crossref_metadata_2025 huggingface dataset:
Modifications to the Gomori acid phosphatase technique for controlled-temperature frozen sections
Authors: Bitensky Lucille
Published: April 2021

The preservation of inert lysosomes in tissue sections depends on the use of the controlled-temperature freezing-sectioning technique. The Gomori procedure for acid phosphatase produces considerable disintegration of these unfixed sections. This disintegration is not due to incubation in the acid medium nor to the rinsing either in dilute acetic acid or in distilled water, but to the treatment with the solution of ammonium sulphide. It is suggested that for this solution there should be substituted a saturated aqueous solution of hydrogen sulphide gas, which does not cause such cellular deformation. Another improvement involves the deletion of the rinse in acetic acid, because this might render soluble some of the specific precipitate in sections showing minimal acid phosphatase activity.
A further note on the use of the Philips ‘mirror-condenser lamp’ in microscopy
Authors: John R.
Published: April 2021

A sheet of ground glass may advantageously replace the glass rod in the adaptation of this illuminant to microscopy.
The form of bivalent chromosomes in newt oocytes at first metaphase of meiosis
Authors: Watson I. D. , Callan H. G.
Published: April 2021

Lampbrush chromosomes in the ovarian oocytes of newts are associated as bivalents. Some connexions between lampbrush chromosomes are chiasmata; others are known to be fusions of gene products; yet others, namely reflected, centromere, and telomere fusions, do not appear to be due simply to the fusion of gene products. Whether chiasmata are involved in reflected, centromere, and telomere fusions cannot be decided from examination of the chromosomes at the lampbrush stage. Bivalents from oocytes at first meiotic metaphase were therefore studied. The oocytes of newts reach first meiotic metaphase after ovulation, whilst they are free in the coelome. Reflected, centromere, and the great majority of telomere fusions do not persist to first meiotic metaphase: thus chiasmata are not involved in them.

In oocyte bivalents of Triturus helveticus chiasmata are not restricted in their distribution, whereas in spermatocyte bivalents of this species chiasmata are proterminally localized. In oocyte bivalents of 3 subspecies of T. cristatus chiasmata are procentrically localized, whereas in spermatocyte bivalents of these subspecies chiasmata are not restricted in their distribution.

Thus in T. helveticus meiosis in the female sex is mainly responsible for genetic recombination, whereas in T. cristatus the situation is reversed. We conclude that to base genetical and evolutionary inferences on information drawn from the meiosis of one sex only is unjustified, and we doubt the validity of the claim that chiasma localization has arisen so as to restrict genetic recombination.
The fine structure of the membranes which cover the egg of the grasshopper, Melanoplus differentialis, with special reference to the hydropyle
Authors: Slifer Eleanor H. , Sekhon Sant S.
Published: April 2021

Electron-microscope studies have shown that the epicuticle of the hydropyle consists of 2 layers. The inner is complexly folded and the outer consists of a meshwork of fine fibrils which fills the spaces between the folds. The endocuticle is laminated, penetrated by pore canals, and contains many wax-canal filaments. The filaments are especially abundant immediately before diapause.

During diapause a dense, homogeneous layer is present at the outer surface of the hydropyle. It is absent before diapause and discontinuous or absent in eggs which are developing without diapause, or after diapause has been prevented or broken. The results confirm the conclusions, based on earlier studies, that the hydropyle is waterproofed by a waxy coating during diapause and that this material is absent or discontinuous in eggs which are developing.

The vitelline membrane is an excessively thin, dense layer which lies below the chorion and lines the micropyles. It is less resistant at the posterior end of the egg than elsewhere. During development it is incorporated into the cuticle, which is secreted by the serosa. It is now believed that the ‘resistant endochorion’ described earlier for this species is identical with the vitelline membrane which Salt described in 1952 for the eggs of Melanoplus bivittatus.
Morphological variability and its physiological origin in oocyte nuclei of the crested newt
Authors: Macgregor H. C.
Published: April 2021

The effects of hypophysectomy and of subcutaneous injection of gonadotrophin upon whole oocytes, oocyte nuclei, and lampbrush chromosomes of the newt Triturus cristatus carnifex have been studied.

Hypophysectomy leads to a reduced rate of incorporation of 32P into the whole oocytes and oocyte nuclei. Large, yolky oocytes are more severely affected than are small oocytes lacking yolk. Hypophysectomy also leads to decreased stiffness of oocyte nuclear sap, change in the number and character of free granules in the nuclear sap, and alteration in the size of certain objects occurring at specific sites on the lampbrush chromosomes.

Injection of mammalian gonadotrophin leads to an increased rate of uptake of 3aP into the cytoplasm and nuclei of yolky oocytes. Gonadotrophin treatment also leads to increased stiffness of oocyte nuclear sap, decrease in the number and/or the size of free granules in the nuclear sap, reduction in size of the giant loops of chromosomes X, XI, and XII, and changes at the axial granule loci of chromosome I and the sphere loci of chromosomes V and VIII.

Each of the features mentioned above varies in nature from one animal to another. This inconstancy, which is superimposed upon stable genetic characteristics and upon those developmental changes which normally accompany oocyte growth, is now shown to reflect differences in the physiological states of the ovaries of different newts.
The cuticle and associated structures of Podura aquatica at the moult
Authors: Noble-Nesbitt J.
Published: April 2021

At the beginning of a moult a foam secretion appears between the epidermal cell surface and the old cuticle. This secretion is involved only with the lifting away of the old cuticle and formation of the exuvial space. A granular secretion then appears in the exuvial space. The granules contain inactive moulting enzymes, which become active only after the completion of the new cuticulin layer, and then digest the soft parts of the old cuticle. The rest of the new cuticle is laid down extracellularly and in lamellae below the cuticulin layer. The sculpturing of the new cuticle occurs under the influence of the epidermal cells. Subsequent hardening of certain areas of the new cuticle involves disruption of the lamellae and complete reorganization. Setae are formed early and rapidly, but nervous connexions with the old setae are maintained until just before ecdysis. Muscle insertions into the new cuticle are formed early, but attachment to the old cuticle is retained until ecdysis. The cuticulin layer is involved in the formation of the new attachments.
An approach to the thermodynamics of histological dyeing, illustrated by experiments with azure A
Authors: Goldstein D. J.
Published: April 2021

Despite extensive quantitative work on the thermodynamics of textile dyeing (Vickerstaff, 1954), probably only Weiss (1954), who estimated the heat of reaction of elastin with orcein in vitro, has attempted to apply similar methods to a histological problem. In the present article a semi-quantitative investigation into the effect of temperature on the staining of sections by the basic dye azure A (M.W. 292) is reported, and certain aspects of the thermo- dynamics of staining are discussed. Despite the fact, discussed in the text, that some of the results reported in the present article can be accepted only with reservations, it will be shown that the thermodynamical approach to staining promises to throw light on several aspects of the staining process.
Electrophoresis of acid dyes
Authors: Byrne Jennifer M.
Published: April 2021

Electrophoresis experiments were performed to find out whether the hydroxy- phthalein dyes which have been found to behave as basic rather than as acid dyes in their staining of phospholipid showed any signs of an amphoteric character.

It was found that it is precisely those acid dyes that stain phospholipids that show least anionic movement in electrophoresis at neutrality.
Cytochemistry of the test cells in the eggs of Pyura squamulosa (Tunicata, Pleurogonia)
Authors: Seshachar B. R. , Venkatasubba Rao S. R.
Published: April 2021

The test cells in the eggs of Pyura squamulosa are rich in PAS-negative acid mucopolysaccharides. They also contain PAS-positive lipoproteins and other carbo- hydrate-protein-lipid complexes. The possible role of sulphated acid mucopolysac- charides in these cells is discussed.
The histochemical demonstration of haemoglobin and haemosiderin in the growing oocytes of a teleost fish
Authors: Chatterjee Nirmala
Published: April 2021

In a previous investigation, evidence was obtained indicating the presence of erythro- cytes in the cytoplasm and germinal vesicle of a teleost fish, Trichogaster fasciatus. Histochemical tests for haemoglobin and related iron compounds have been applied to verify the histological and cytological findings. Haemoglobin (both intact in the erythrocytes and in the crystalline state) and pseudoperoxidase granules have been demonstrated histochemically both in the ooplasm and in the nucleus of immature eggs. Haemosiderins have also been detected and histochemically localized in and around the ooplasmic vacuoles.
Elementary neurosecretory granules in the neurones of the snail, Helix aspersa
Authors: Lane Nancy J.
Published: April 2021

Elementary neurosecretory granules are present in the cytoplasm of certain neurones of the snail, Helix aspersa. The granules appear to be elaborated within the lamellae of the Golgi complex and produced at the edges of the lamellae by budding and vésiculation.
The demonstration of lysosomes in mouse skin
Authors: Diengdoh J. V.
Published: April 2021

Lysosomes, as demonstrated biochemically in the liver, are subcellular particles containing a group of hydrolytic enzymes enclosed by a membrane-like barrier. They are apparently inactive in the normal state, but when subjected to various forms of injurious treatments the enzymes associated with them are released. The existence of lysosomes in skin is demonstrated in the present communication. The resistance of this tissue to homogenization makes the biochemical study of lysosomes very difficult. Yet, by the application of histochemical methods to sections of skin, it has been possible to use the same criteria as would be employed in the biochemical characterization of these organelles. By using the controlled-temperature freezing-sectioning method it has been possible to obtain frozen sections in which cytoplasmic particles could be demonstrated which were enzymically inactive for acid phosphatase until the sections were subjected to such injurious treatments as heat, repeated freezing and thawing, hypotonic solutions, distilled water, and ‘triton-X-100’. Since the subcellular particles demonstrated behaved in the same manner as lysosomes prepared biochemically from liver, it is concluded that the cytoplasmic organelles staining for acid phosphatase in mouse skin are lysosomes as biochemically defined.
On bridging the gap in cytology between the light and electron microscopes by some combined observations on snail neurones
Authors: McGee-Russell S. M.
Published: April 2021

Discrepancies between observations made with the light microscope only, and with the electron microscope only, can be clarified by using both instruments to study exactly the same section of the same object. A simple technique for doing this is outlined. Direct, phase-contrast, ‘anoptral’ phase-contrast, dark-ground, interference, and ultra-violet microscopy can all be used. When applied to snail neurones this technique of combined observations reveals intracellular organelles which have not previously been differentiated. These organelles are positively identified by criteria appropriate to each instrument. By combined observations it is possible to see the ‘Golgi apparatus’ in preparations stained only with Nile blue, by direct microscopy. Data obtained by combined observations are considered in relation to the previous literature. Unequivocal cross-correlations between the light and the electron microscope go a long way towards explaining past difficulties.
Experiments on embedding media for electron microscopy
Authors: McGee-Russell S. M. , De Bruijn W. C.
Published: April 2021

Experiments were conducted to determine the feasibility of improving the trimming and sectioning properties of the polymers glycol methacrylate (Rosenberg, Bartl and Leško,1960) and durcupan (X133/1097) (Stäubli, 1960) by combining them with other resins, in particular epon 812. We have also attempted to determine the value of comparative studies of tissue given different fixation and dehydration treatments, prior to embedding in the same final embedding medium.
Surface reflexion interference microscopy of bull spermatozoa
Authors: Iversen Simon
Published: April 2021

This type of microscopy gives absolute measurements of the vertical dimension and configuration of an object. As an example bull spermatozoa were used and measurements showed the vertical dimension and thus the volume to be considerably smaller than obtained by other methods.
Presumed photoreceptive cilia in a ctenophore
Authors: Horridge G. A.
Published: April 2021

Four groups of lamellate bodies are symmetrically arranged inter-radially in the floor of the apical organ. Each is composed of many streamed-out membranes of a group of about a dozen cilia, within an invagination of a cell. The rings of ciliary fibrils, of the 9 + 0 pattern, become disarrayed not far from the base. Their dense membranes are lined with granules so that the successive lamellae resemble those of the modified cilia of vertebrate eyes, although flattened in a different plane. On this basis, of ciliary origin, and their resemblance to photoreceptors in fine detail, these structures are interpreted as photoreceptors.
Acid phosphatase activity in the neutral red granules of mouse exocrine pancreas cells
Authors: Byrne Jennifer M.
Published: April 2021

The Gomori test for acid phosphatase was performed on pancreatic tissue from mice injected with neutral red. On an electron microscopical level, acid phosphatase activity was found to be localized in the neutral red granules.

It is suggested that the neutral red granules are of lysosomal derivation.
The yolk nucleus of fish oocytes
Authors: Nayyar R. P.
Published: April 2021

A comparative study of the yolk nucleus in the oocytes from 8 species of fishes has been carried out. The yolk nucleus appears as a mass of lipid granules and mitochondria situated beside the nucleus. It becomes spherical, detaches itself from the nucleus, and migrates to the peripheral region of the cytoplasm to lie just below the cell membrane. During the migration, the lipid granules of the yolk nucleus grow and move out of this organelle. When the oocyte is about 180/x in diameter, the yolk nucleus breaks up and its components are dispersed in the cytoplasm. No differences have been found in the morphology of the yolk nucleus in the species under investi- gation.
Two more accessories for the Huxley ultramicrotome
Authors: Mcgee-Russell S. M. , Smale C. J. G. , Banbury W.
Published: April 2021

A combined section-mounting stage and miniature hot plate has been made to be used with the Huxley ultramicrotome. It facilitates precision in the handling of 0·2 to 2 μ sections during mounting and staining for light microscopy. Both processes can be carried out under continuous binocular magnification.

The advance mechanism of the microtome has been fitted with a simple bell circuit to give an audible signal at the beginning and end of the full travel of the mechanical advance. This signal may be calibrated by readings on the vernier advance of the knife holder, for re-setting the microtome on a given block face. During prolonged bouts of sectioning the audible signal is a useful warning of full extension of the advance mechanism.
The connective tissue sheath of the locust nervous system: its development in the embryo
Authors: Ashhurst Doreen E.
Published: April 2021

The embryological development of the connective tissue sheath around the nervous system has been investigated in Schistocerca gregaria. The sheath cells appear to be derived from outlying ganglion cells. The neural lamella is first visible when the embryo is 9 days old and it increases in thickness until hatching occurs on the twelfth day. It is produced entirely by the sheath cells.

The sheath cells have numerous lipid droplets in their cytoplasm. Some neutral mucopolysaccharide and proteins are also present. The histochemical reactions of the neural lamella after its formation suggest that it is composed of collagenous proteins embedded in neutral mucopolysaccharides.

The sheath cells are typical fibroblasts during the formation of the neural lamella. The cisternae of the endoplasmic reticulum are dilated into vesicles which contain a somewhat electron-dense material. No intracellular fibrils were observed. Collagen fibrils with banding of periodicity between 55 and 60 mμ are seen in the neural lamella from 11 days onwards.
The Distribution of Alkaline Phosphatase in the Skull of the Developing Trout
Authors: Lorch I. Joan
Published: April 2021

The histological and cytological distribution of alkaline phosphatase in developing trout has been studied with special reference to membrane and cartilage bone formation in the skull. Nuclear phosphatase is widely distributed in the youngest stages examined, but decreases as differentiation proceeds. Extracellular phosphatase is always associated with ossification or fibre formation. No deposition of calcium salts in the absence of phosphatase was observed. Alkaline phosphatase is probably connected with histogenesis in general apart from its special function in calcification.
The Shell in the Lamellibranchia
Authors: Owen G.
Published: April 2021

I. In the Lamellibranchia, the direction of growth at any region of the valve margins may be resolved into : (a) a radial component radiating from the umbo and acting in the plane of the generating curve ; (b) a transverse component acting at right angles to the plane of the generating curve; (c) a tangential component acting tangentially to, and in the plane of, the generating curve. The radial component is always present and affects the form of both valves while the transverse component may be reduced or absent in one valve.

2. The lamellibranch mantle/shell is orientated with reference to the normal axis. This normal axis follows that sector of the shell secreted by the normal zone of the mantle edge (i.e. where the effect of the transverse component is greatest) and passes through the umbo, the normal zone and the point at which the greatest transverse diameter of the shell intersects the surface of the valves.

3. The form of the shell valves should be considered with reference to : (a) the outline of the generating curve; (b) the spiral angle of the normal axis; (c) the form (i.e. pianospiral or turbinate spiral) of the normal axis.

4. The ‘deflection’ anteriorly of the umbones and the splitting of the anterior portion of the ligament in many bivalves is a consequence of a tangential component affecting the form of the valves.

5. In both gastropods and lamellibranchs, the turbinate spiral shell is the resultant of two differential growth ratios. In the Gastropoda, however, both ratios act perpendicularly to the plane of the generating curve, while in the Lamellibranchia, one acts perpendicularly to this plane while the other acts in the plane of the generating curve.
A Histological Study of the Development of the Scales of the Largemouth Black Bass (Micropterus salmoides)
Authors: Dietrich Mary Alice
Published: April 2021

1. The scale method of age determination in largemouth black bass, Micropterus salmoides, is valid at least up to and probably including the third year of the fish’s life. A more careful study of older fish might reveal that it was valid beyond that point.

2. The annulus in a largemouth black bass is formed by a brief but gradual slowing down of growth and then its quick resumption. The annulus appears as a wide band on the anterior edge of the scale, and as a dark line (circulus) cutting across some inner dark lines (also circuit) on the lateral edges.

3. The scale is mesodermal in origin, and lies in a pocket surrounded by dermal tissue, which in turn is covered externally by a thin layer of epidermis.

4. The bony layer is formed by osteoblastic cells on its outer surface in a manner similar to the formation of dermal bone. Excess bony material is accumulated in ridges or circuli.

5. The fibrillary plate is formed by the fibroblastic cells on its inner surface.
Nematocysts of Corynactis: The Activity of the Filament during Discharge
Authors: Robson E. A.
Published: April 2021

1. The appearance of one type of nematocyst from Corynactis before, during, and after discharge is described. Discharge is a progressive eversion of the intracapsular filament.

2. Weill’s observation that the speed at which dried nematocysts can be made to discharge depends on the quantity of water available is confirmed.

3. In water, dry isolated fragments of undischarged filament undergo changes in size which normally accompany discharge, while remaining uneverted. This reaction is an anisometric swelling of the shaft wall due to water absorption, and is largely responsible for the normal progression of discharge in nematocysts.

4. Electron microscopy has been used to investigate the morphology of various nematocysts.
Observations on Substances that react weakly to the Periodic Acid/Schiff Test
Authors: Hale Arthur J.
Published: April 2021

It has been shown that certain mucinous substances which are weakly positive with the periodic acid/Schiff technique stain more strongly after treating them with a solution of sodium hydroxide.

The deepening of the staining reaction is produced by making available, for aldehyde production by periodic acid, more .CHOH.CHOH., . CHOH. CHNH2., or . CHOH .CHNHR. groups. This is done without affecting those sulphate or metaphosphate groups responsible for metachromasia.
The Lipoid Contents of the Golgi Bodies in the Oocytes of the Indian Water Spider, Lycosa birmanica
Authors: Krishna Daya
Published: April 2021

1. The Golgi bodies of the oocyte of Lycosa birmanica do not contain triglyceride.

2. They contain phospholipine, lipo-protein, and protein.

3. They are granular and all of approximately equal size. Any variation in their size or shape is due to the irregular deposition of phospholipine on them.

4. Fine bodies resembling Golgi bodies in appearance and reacting like them with osmium tetroxide and silver nitrate consist of phospholipine.

5. The Golgi bodies in the material studied appear not to multiply by division, but to arise in the ground cytoplasm independently of one another. They may be regarded as nutritive bodies.
The Cell-theory: a Restatement, History, and Critique: Part IV. The Multiplication of Cells
Authors: Baker John R.
Published: April 2021

In the first half of the nineteenth century it was commonly supposed that new cells arose either exogenously, outside pre-existing cells, or endogenously, from small rudiments that appeared within pre-existing cells and gradually grew larger. The theory of exogeny had been founded by Wolff (1759), and was supported especially by Link (1807), Schwann (1839), and Vogt (1842). The theory of endogeny, which had been hinted at by various writers in early times, obtained the backing of a very large literature. Its chief advocates were Raspail (1825, &c.), Turpin (1827, &c.), Schleiden (1838), Kôlliker (1843-4), and Goodsir (1845).

That cells do not arise exogenously or endogenously, but are produced by the division of pre-existing cells, was at last realized by the convergence of studies made in three separate fields, as follows :

(1) Trembley (1746, &c.), Morren (1830, 1836), Ehrenberg (1830, 1832, 1838), and others noticed how protists multiply.

(2) Dumortier (1832), Mohl (1837), and Meyen (1838) watched the partitioning of the cells of filamentous algae.

(3) Several observers studied the cleavage of eggs and at last revealed that this was a process of cell-division (Prévost and Dumas (1824), von Siebold (1837), Barry (1839), Reichert (1840), Bagge (1841), Bergmann (1841-2)).

Nàgeli (1844, 1846) also made an important study of cell-division in all the main groups of plants (except bacteria), but used an unfortunate nomenclature that tended to obscure the true nature of the process.

Remak (1852 and 1855) and Virchow (1852, 1855, 1859) made general statements to the effect that division is the standard method by which cells multiply. The writings of Remak on this subject were much more weighty than those of Virchow.
Physical Factors involved in the Vertical Migration of Plankton
Authors: Harris John E.
Published: April 2021

It is suggested that vertical migration is an inescapable consequence of the use of light by planktonic forms as a means of attaining a level within the euphotic zone; no other sense organ appears capable of producing this result. The mechanism of light response in Daphnia fulfils the necessary requirements for vertical migration, and field observations on other species suggest the presence of similar if not identical physiological features in them. These features are a positive photokinesis which is combined with negative geotaxis at low light intensities; at a critical higher value of light intensity a typical dorsal light reflex cuts off the vertical rise. The dorsal light reflex is probably a response to illumination of the eye within the critical cone of submarine illumination, and is therefore not related to the direction of a particular light source such as the sun.
Histological and Polarization Studies of the Brush Border of the Proximal Convoluted Tubules of the Rat Kidney
Authors: Brewer Douglas B.
Published: April 2021

The kidneys of rats were examined histologically after the intraperitoneal injection of haemoglobin and also after the intrarenal injection of a graphite suspension. During haemoglobin excretion spaces can be seen running across the brush border of the proximal convoluted tubules. These spaces are filled by the reabsorbed haemoglobin passing from the tubular lumen into tbe.tubular cells. After intratubular injection of a graphite suspension, particles about 0·5 μ diameter cross the border and appear in the cell cytoplasm.

Examination with the polarizing microscope shows the brush border to have positive form and negative intrinsic birefringence with respect to the length of the striations.

These findings are considered in relation to the appearances found on electron microscopy. It is suggested that on present evidence it is most likely that the brush border consists of rodlets of the order of 300–600 Å diameter, with an orientated molecular structure at right angles to their length. These rodlets are gathered in tufts so that they diverge from one another. The spaces between the tufts at their bases is about 0·3–0·5 μ and at their tips they just touch one another.
The Deposition of the Third Instar Larval Cuticle of Calliphora erythrocephala
Authors: Wolfe L. S.
Published: April 2021

A histological study has been made of the formation of the cuticle of the third instar of Calliphora.

Increase in size of the epidermal cells and nuclei, particularly in the spiny regions, preceded the release of the moulting fluid. The cytoplasm first became vacuolated and this was followed by the appearance of many granules. The basement membrane is constituted in part by stellate tracheoblast cells. The membrane breaks down just before cuticle deposition and reappears after ecdysis.

The outer epicuticle is formed from coalesced droplets aligned at the cell surface to form a delicate continuous, folded, acidophil, lipoprotein layer. Further, protein and lipoid (cuticulin) is added beneath this layer from cytoplasmic processes to form the inner epicuticle. These processes later became the pore canals. Endocuticle is secreted as filaments from the epidermal cells between and around the processes.

During moulting, phenolic substances and oxidase are transported to the inner epicuticle only in the cuticular spines. Wax and cement layers are not formed and there are no dermal glands.

The peak in the secretory cycle of the oenocytes corresponds to the time of deposition of the epicuticle and the secretory material shows similar staining properties to epicuticular material. The oenocyte groups are connected with each other and with the epidermis by cytoplasmic extensions, through which secretory granules pass.

The muscle insertions are not attacked by the moulting fluid. They are thought to contain protein-bound sulphur. The separation of the muscle insertions and sensory organs from the exuvial cuticle occurs just before ecdysis.

The nature of the epicuticle and the theory that the oenocytes are associated with its formation is discussed.
A Plastic Lacquer Substitute for Coverslips
Authors: Perry J. S.
Published: April 2021

A plastic lacquer manufactured by Cellon Ltd. has been found useful for covering sections on glass slides of any size.

It takes the place of both mounting medium and coverglass and saves storage-space. The method has proved particularly valuable in mounting large series of sections and serial sections of large specimens. Its use in conjunction with bulk staining techniques is described. The lacquer is very clear and has not been found to deteriorate on the slide after several years.
The Thickness of the Cortex of the Sea-Urchin Egg and the Problem of the Vitelline Membrane
Authors: Mitchison J. M.
Published: April 2021

The gelated cortex of a sea-urchin egg can be seen as a granular layer at the edge of the hyaline zone in a centrifuged egg. Measurements were made of the thickness of this layer in the eggs of Paracentrotus lividus and Arbacia lixula at various stages of development from the unfertilized egg to the first cleavage. The thickness was roughly 2 μ in living eggs, and 1 · 15 – 1 · 35 μ in sections of fixed eggs. There were no appreciable changes in the thickness up to the first cleavage, and it is concluded that a value of 1 · 5 μ can be taken as an approximate figure for all stages.

The cortex is usually invisible in normal eggs either living or in section, but in the case of sections of fertilized Arbacia eggs it can be seen as a vacuolated layer. The thickness of this layer was found to be 1 · 13 μ at the sperm aster stage and 1 · 50 μ at cleavage. In these eggs at cleavage, there were no signs either of differences in thickness at different regions of the surface or of a differentiated region of the cytoplasm ahead of the furrow.

There were no clear indications of the presence of a vitelline membrane either in living or fixed eggs.

A layer about 0 · 8 μ thick, pale with iron haematoxylin, was found at the edge of sections of unfertilized eggs which had been fixed in Bouin, but not with those which had been fixed in Flemming. This is probably the outer layer of the cortex which normally contains the cortical granules.
The Site of Damage in Amoebae Exposed to Lethal Concentrations of Methyl di-(β-Chloroethyl)-Amine (a ‘Nitrogen Mustard’)
Authors: Ord M. J. , Danielli J. F.
Published: April 2021

The technique of nuclear transfer in Amoeba proteus was used to study the extent to which methyl di-(β-chloroethyl)-amine damages nucleus and cytoplasm. Results obtained showed that cytoplasm was damaged directly by the drug; exposure of normal cytoplasm to nuclei damaged by β-chloroethylamine for up to 3 days caused no lethal damage. Nuclei were probably directly damaged, but could also be damaged by injured cytoplasm, normal nuclei being lethally damaged when exposed to injured cytoplasm for only 2 hours. Death from lethal cytoplasmic damage generally occurred within a few days; animals with lethally damaged cytoplasm seldom divided. Death from lethal nuclear damage was delayed in some cases for as long as 6 weeks, such nuclei being able to divide once or twice before death.
The Fate of ‘Thorotrast’ (Thorium Dioxide) injected into the Dorsal Lymph Sac of the Frog, Rana temporaria
Authors: Foxon G. E. H. , Rowson K. E. K.
Published: April 2021

Thorotrast (a colloidal suspension of thorium dioxide) injected into the dorsal lymph sac of the common frog, Rana temporaria, can be shown by radiological methods to pass through the anterior lymph hearts and so into the blood system. From the blood the thorotrast is removed, as in mammals, by cells of the reticulo-endothelial system and by macrophages, the sites of greatest activity being the liver, spleen, and bone-marrow. Whereas in mammals almost all uptake of such colloidal substances takes place in these organs, in the frog there is considerable macrophage activity elsewhere, notably in the submucosa of the alimentary canal. Our results suggest that macrophages which ingest thorium particles in the wall of the alimentary canal migrate through the blood system to the liver where the thorium is ultimately deposited. This may be correlated with the possession by the frog of a macrophage and reticuloendothelial system less highly organized than that possessed by mammals.
The Histochemical Recognition of Phenols, especially Tyrosine
Authors: Baker John R.
Published: April 2021

Sections of tissue embedded in collodion are heated in an acidified aqueous solution of mercuric sulphate and sodium nitrite. A red colour denotes the presence of phenols (generally the tyrosine of proteins). The reagent is more rational than Millon’s and most of the modifications of his method used up till now in histochemistry. It gives a particularly strong coloration.
The Morphology of the Golgi Bodies with reference to Secretion in the Liver-cells of the Slug, Anadenus altivagus, as seen under the phase-contrast Microscope
Authors: Rishi Rajinder
Published: April 2021

Golgi bodies in the living liver-cells of the slug, Anadenus altivagus, exist in two forms: (a) homogeneous granules or spheres of dark contrast, and (b) spheres showing a duplex structure with a light greyish internum and a dark externum, which may be single or composite. The greyish internum of these duplex spheroids grows into the secretory granules, the dark externum disappearing in the process of growth. Mitochondria appear as fibres of light greyish contrast with a dark granule at each tip. This dark granule disassociates itself from the mitochondrion and forms the Golgi granule of dark contrast—the Golgi ‘pre-substance’. The Golgi pre-substance, stainable with neutral red, forms the Golgi spheroids.
Mitotic Activity during the Early Differentiation of the Scleral Bones in the Chick
Authors: Hale L. J.
Published: April 2021

The dispositions of mitoses in the mesenchyme beneath the conjunctiva of parts of a 7-, 8-, 9-, and 10-day embryo have been ascertained. For the purpose of analysis, the number of mitoses, cell population density, and mitotic index have been found in small segments of annuli which include parts of the rings of bone primordia, and the mesenchyme between them. Twenty-three primordia were studied.

It is found that the cell population density increases from about 4−14 × 105 per cubic mm within the primordia, but only from about 4−9 × 105 in the mesenchyme between them.

Mitotic activity increases sharply within young primordia from about 12-27 mitoses per 1,000 cells, and thereafter decreases. It is found that this mitotic activity probably occurs in three waves of decreasing intensity. Between the primordia mitotic activity is at a markedly lower level and probably follows a simpler pattern.

The cells involved in this mitotic activity in the primordia are particularly those just beneath the conjunctival papilla, and the number of mitoses decreases the greater the distance from the conjunctiva. In the 8-and 9-day embryos, the number of mitoses is inversely proportional to the distance.

Calculation indicates that in each of the three waves of cell division, the cells that divide do so only once; and that this mitotic activity is adequate to account for the increase in cell population density which is found.

The cause of the increase in the number of cell divisions in the primordia is not clear, but the result is probably the production of blastemas, the cells of which become the osteoblasts of the scleral bones.
Mesodermal Cell Deaths during the Early Development of the Scleral Bones in the Chick
Authors: Hale L. J.
Published: April 2021

The positions of degenerating cells in the mesenchyme of the scleral bone pri- mordia of the chick, and in the fibrous sclera beneath them, have been ascertained. It is shown that the number of cell deaths within the bone primordia, and also beneath them in the fibrous sclera, is markedly higher than, and follows a different pattern from the regions between. A centre of cell destruction is seen to occur at and near to the boundary of the mesenchyme and fibrous sclera. This begins in 7- to 8-day primordia, rises to a peak at 8 to 9 days, and subsides in 9- to 10-day primordia. A second centre of cell death occurs in the mesenchyme nearer to the conjunctival papilla. It starts in 8- to 9-day eyes about mid-way between the conjunctiva and sclera, and as it increases in intensity, the centre moves nearer to the conjunctival papilla (9 to 10 days), beneath which it appears to subside (some 10-day primordia). The function of these waves of cell destruction is discussed. It is concluded that their most likely function is morphogenetic; they may make a space into which the osteogenic cells migrate, or they may ensure a normal position and shape for the developing bone. Consideration has also been given to the possibility that the products of cell death might have a histiogenetic function.
Studies of Serpulid Tube Formation: I. The Secretion of the Calcareous and Organic Components of the Tube by Pomatoceros triqueter
Authors: Hedley R. H.
Published: April 2021

Calcium carbonate, in a finely granular form, is secreted into the fold of the peristomial collar by a pair of tubulo-racemose glands in the peristomium.

Most of the organic material of the tube is secreted by the ventro-lateral epithelial cells which surround the main ducts of the calcium-secreting glands. These cells are always filled with a basiphil mucigen which contains some free a-glycol groups. This material retains its affinity for basic dyes and for ferric iron at a low pH. The affinity for iron is retained when the pH is low enough to exclude carboxyl and phosphoric acid groups from the reaction and it is probable that the sulphuric acid groups are responsible..

The reactions of this mucigen to histochemical tests together with the similarity in behaviour of a precipitated heparin preparation make it likely that the material is a sulphomucopolysaccharide.
The Growth and Development of a Viviparous Compound Ascidian, Hypsistozoa fasmeriana
Authors: Brewin Beryl I.
Published: April 2021

The viviparity recorded for this ascidian parallels that of placental mammals in reduction of the number and size of the eggs, the development of extra-embryonic membranes, and the prolongation of larval development with increase in the gestation period.

The ovum is alecithal, 25 μ. in diameter; it develops within an oviducal brood pouch in which the lining cells become distinctly modified and which remains attached to the parent for 5! months.

Exposure of the embryo to the lumen of the pouch is brought about by rupture of the overlying follicle cells due to enzyme secretion by the dorsal-most cells of the blastula.

Endodermal development is precocious. At the gastrula stage the future oesophageal region, the future stomach, and a pair of endodermal tubes are distinguishable.

The paired endodermal tubes are unique in the ascidians. They are larval structures which disappear after metamorphosis and bear no relation to the functional stigmata of the oozooid. They resemble the branchial tubes of the Appendicularia, developing as blind outgrowths which later open through to the exterior ; but in this species they open dorsally, not ventrally. They act as passive channels through which material from the pouch passes into the gut (a bolus being present from the gastrula stage onwards) and as anchoring strands for the ectotrophe.

This extra-embryonic membrane formed by elevation of the dorsal ectoderm ultimately practically envelops the embryo and becomes apposed to the lining of the pouch. It is extremely simple, exhibits no vascularization, makes no actual liaison with the oviducal epithelium, and shows little cell differentiation.

Extra-embryonic material reaches the embryo indirectly by diffusion across the ectotrophe (which unlike the remaining embryonic ectoderm secretes no test), and directly through the endodermal tubes. The latter method is the more important during early stages of development, the former during later stages.

The production of an extremely large and complex tadpole with numerous buds at an advanced stage of organogenesis testifies to the success of this type of viviparity.
On the Origin of the Electric Organ in Malapterurus electricus
Authors: Johnels Alf G.
Published: April 2021

The present study was made on two small specimens of Malapterurus electricus, of standard lengths n.4 and 12.7 mm. As is well known, the postembryonic growth of electric organs in Malapterurus and other electric fishes takes place by an enlargement of the electric units and not by an increase in the number of the electric plates. In the present material, however, there is a multiplication of electric tissue elements in the rostral portion of the electric organ. The structure of this multiplication zone is described. In the anterior region the connective tissue membranes which surround the two halves of the electric organ form structures similar to tendons which are fixed to the ventral surface of the shoulder girdle on each side of the median line. A small deficiency on each side in the muscular wall in the same region was observed in adult specimens by Maurer. This deficiency is more evident in the young specimens studied in the present paper and it is covered from the outside by the multiplication zone of the electric organ. In this place the electric nerve joins the electric organ. The giant electric cell, the surface of which is penetrated by intracellular capillaries, is situated in the anterior part of the spinal cord and its axon emerges with the third ventral spinal root. In the multiplication zone the connective tissue membranes are completely independent of the dermal connective tissue and the space between the electric organ and the skin is of a conventional subdermal type. These circumstances strongly indicate that the electric organ is of myoblastic origin in Malapterurus as in all other electric fishes known in this respect. Nothing has been observed which supports the idea of an adenoid origin of the electric organ in Malapterurus.
Formation and involution of striated muscle fibres during the growth and moulting cycles of rhodnius prolixus : (hemiptera)
Authors: Wigglesworth V. B.
Published: April 2021

The ventral intersegmental muscles of the abdomen in Rhodnius undergo a cycle of development and involution during each larval stage. They are fully developed only at the time of moulting or hatching from the egg. Within 3 or 4 days after moulting the fibrils have disappeared ; but the nuclei, with a little cytoplasm containing mitochondria, survive within the highly folded muscle-sheath.

The formation of fibrils begins between 2 and 3 days after feeding. At first they are uniformly birefringent. The striations appear later, and the muscles will then contract after transection. The fibrils are 0·1–0·2μ thick when first formed; they grow by intussusception and splitting to a thickness of about 0·8 μ.

Succinoxidase first appears in quantity in the mitochondria at the time when striation and contractility develop. It disappears within 3 days after moulting, during the involution of the fibrils. The distribution of ribonucleic acid in the developing muscle is described.

Involution results from autolysis which begins around the nuclei in the centre of the muscle. The phagocytic blood-cells play no part in the break-down.

The rich nerve-supply to the muscles persists apparently unchanged throughout the cycle of involution; and the cycle of growth occurs normally after section of the nerves.
A Note on Insect Wing Veins and their Tracheae
Authors: Smart John
Published: April 2021

Experiments involving interference with the tracheae of the nymphal fore-wing pad of the American cockroach (Periplaneta americana (Linn.)) are described and the results discussed. It is concluded that the pattern of the tracheae is not immutable and so cannot be regarded as fundamental in determining the pattern of the imaginai wing-venation ; the pattern may, however, continue to be used, in the first instance, as a guide to the more fundamental pattern of the lacunae that precede the veins.
The Growth of the Trout Retina
Authors: Lyall A. H.
Published: April 2021

I. The growth of the trout eye is negatively allometric in relation to body-length.

The relative thicknesses of the retinal layers, and their cell densities, change as the eye grows. The addition of new cells takes place from a peripheral growth zone. Measurements from a wide size-range of trout retinae show that the dimensions of the cone pattern increase as the retina grows. The relative importance of these two processes changes as the eye grows; in early growth the addition of new cells is the principal factor, but the enlargement of the cone pattern, which occurs at an almost constant rate throughout growth, becomes more significant later.
Osmichrome Fixation
Authors: ELFTMAN HERBERT
Published: April 2021

Fixation by the combined action of osmium tetroxide dichromate involves the use of two reagents which produce their best results at two different hydrogen ion concentrations. By applying them in sequence the conditions may be adjusted independently for the two reagents. For tissues of the rat the following schedule has provided good results: (1) Fix for 5 to 7 hours at 5° C in 1% osmium tetroxide buffered at pH 7.2; (2) rinse briefly; (3) chromate for 18 hours at 20° C in 2.5% potasium dichromate dissolved in 5% mercuric chloride; (4) embed in parafin.
A Histochemical Study of the Connective Tissue-Fibres in the Leech, Glossiphonia complanata
Authors: Bradbury S.
Published: April 2021

The fibres and the connective tissue ground-substance of Glossiphonia complanata have been studied morphologically and histochemically. The fibres, which run in the connective tissue-substance between the organs of the body, are cytoplasmic extensions of bipolar or multipolar cells. The average diameter of the fibres is between 1 and 2 μ, and a single fibre may exceed 100 μ in length. Each fibre is differentiated into a cortex and a medulla. The cortex contains arginine, and some acid and neutral mucopolysaccharides ; this suggests that it is collagenous. The medulla is an extension of the protoplasm of the cell-body.

The cell-body of the fibre has a basiphil cytoplasm which contains arginine, acid and neutral mucopolysaccharides, and much ribonucleic acid. Spherical lipochondria up to 4 μ in diameter are present in the cytoplasm, especially near the nucleus ; they contain chiefly phospholipid. Threadlike mitochondria are present in the cytoplasm of this cell.

The connective tissue ground-substance is present as a matrix between the cells and organs of the body. Histochemical tests showed that it contains small amounts of arginine, tyrosine, neutral and acid mucopolysaccharides. The refractive index of the ground-substance is about 1·35.