method by which it may be formed synthetically. In the newt the corresponding acid is contained in globules which have the microscopic appearance of milk-globules, but differ from them chemically by being soluble in water. The physiological properties of the poison of the salamander are the same as those of that of the scorpion, and resemble those which have been observed with amylcarbylamine. The author has not yet studied the poison of serpents, but he thinks that they have probably the same kind of constitution. The general biochemical mode of formation may be thus defined. Every amidecompound, whether simple or a peptone, may fix the elements of formic acid in the nascent state, and give rise to a carbyl-compound of toxic properties and unstable in composition. Every methyl group which is insufficiently destroyed by oxidation gives rise not to carbonic but to formic acid, and so furnishes the elements of the carbyl-compound. Development of Lacerta_agilis.*-H. Strahl gives a further account of the developmental process at the anterior end of the embryo of Lacerta. In a previous communication by the same author it had been pointed out that the head of the embryo consists up to a comparatively late period of ectoderm and endoderm only, the mesoderm being entirely absent. Some of the more important results of the present communication are as follows:-The vascular area which is at first only developed at the sides of and behind the embryo grows forward and unites above the head to form a single oval disk; before this has taken place the cleavage of the mesoderm is visible in the anterior margins of the vascular area, and the fusion of the two cavities thus formed leads to the uniting together of the two sides of the vascular area. The larger anterior portion of the amnion is formed by growth from before backwards without any lateral folding of its ectodermic layer. The formation of the false amnion is very different from its formation in the chick; in the latter the folds of the splanchnic layer of the mesoderm and of the endoderm appear before the complete closure of the amnion, while in the embryo of Lacerta, these same folds which inclose the embryo, and may therefore be termed the false amnion, appear after the closure of the amnion. Another difference between the embryo chick and the embryo lizard is to be found in the relation between the closure of the body-cavity and the closure of the head intestine; in Lacerta the body-cavity closes almost immediately after the closure of the intestine, while in the chick the ventral sides of the body-cavity remain separate from each other long after the closure of the intestine. The twisting of the embryo on to the left side causes a like twisting of the anterior portion of the amnion, which is by this time entirely closed; at the posterior end of the embryo, where the two folds of the amnion have not yet become united, this twisting of the amnion does not take place, inasmuch as the left fold grows more rapidly than the right, and so the two, when they come to unite, remain in the same place as the egg membrane, and do not participate in the twisting of the embryo. *Arch. f. Anat. u. Physiol. (Anat. Abtheil.), 1884, pp. 41-88 (2 pls.). Development of Teleostei.-C. Kuppfer continues his studies on the development of the Vertebrata, and treats of the Teleostei. Two varieties of trout were selected for study. The blastoderm on the eighth day presented a round area with a prominent knob at the posterior extremity (Schwanzknospe); in front of this lies the embryonic shield. The next step is an invagination upon the surface of the latter, exactly as in birds and reptiles, forming a longitudinal farrow which subsequently is crossed at right angles by another furrow; this transverse furrow is only a temporary structure, and presently vanishes, leaving only the longitudinal furrow; at the hinder end of the primitive streak, its margins unite to form a median axial band, which extends as far as the caudal knob. By the beginning of the twelfth day the primitive streak had disappeared, and the axial band a little wider at its anterior extremity occupied the middle line of the embryonic shield coinciding exactly with the anterior extremity of the primitive streak. The disappearance of the primitive streak coincides in point of time with the enclosure of half the yolk within the blastoderm; when the cells of the blastoderm pass beyond the equator of the egg, the primitive streak is entirely replaced by the axial band. At the time of the appearance of the head, the axial band becomes slightly coiled; the "head" consists of the rudiment of the brain and eyes, and one pair of visceral arches; it is developed independently of the primitive streak; though the brain is continuous with the axial band, it is marked off from it by a constriction. The provertebræ which next appear are formed from the axial band, and the anterior ones are developed before the posterior ones; in many other Teleostei the first pair of protovertebræ are situated more in the middle and the process of growth extends forwards as well as backwards. No other pairs of visceral arches are developed in the neighbourhood of the first. The earliest rudiment of the spinal cord appears as a new formation upon the axial band, and is continuous with the brain; the central cavity of both, which is a secondary formation, commences in the eyes and passes down the brain into the spinal cord; this central cavity shows widenings here and there in the brain which do not correspond to the subsequently formed ventricles. Influence of High Pressures on Living Organisms.t-P. Regnard has been able to make some experiments with a press giving a pressure of 1000 atmospheres; he finds that under such pressures as obtain on the bed of the ocean, plants, infusoria, molluscs, annelids, and crustacea fall into a somnolent condition, or one of "latent life"; fishes, when exposed to similar pressures, die. Experiments made show that muscles of the frog increase in weight after being subjected to a pressure of 400 atmospheres, but it is not yet known whether this change is chemical or physical. Interesting points of resemblance are to be detected between these results and those obtained by the Talisman' deep-sea explorations; *Arch. f. Anat. u. Physiol. (Anat. Abtheil.), 1884, pp. 1-40 (2 pls.). Milne-Edwards has remarked that below 2000 metres the fauna changes. Observations should now be made on the characters of the animals that are brought up dead from great depths; the causes ought to be comparable, though of course of a converse nature, to those that operate on animals subjected to artificial compression. B. INVERTEBRATA. Intracellular Digestion of Invertebrates.-E. Metschnikoff insists on the necessity of collecting physiological as well as morphological evidence before discussing the evolution of any system of organs. The author offers some answers to the question whether the lowest Metazoa have not retained the power of using any or all the cells of their body for the purpose of ingesting food, and commences with ingestion by ectodermal cells. Sponges, unfortunately, are not well suited for observations on the activities of ectodermal cells, and as yet there is no very definite evidence in favour of intracellular digestion by the ectodermal cells of those Metazoa. If powdered carmine be suspended in the water surrounding a Plumularia, a considerable quantity will soon enter the substance of the ectoderm by the nectocalyces, which send out various kinds of pseudopodia; in some cases these may be seen eating up, by means of their ectoderm, the dying hydranths of a colony of Plumularia; the food thus taken in remains in the ectoderm and is not passed on into the endoderm. Actinic also exhibit ectodermal digestion, and gastrula have sometimes been observed which are asymmetrical in form and dirty in appearance, owing to the ingestion by their outer cells of a large quantity of foreign matter; the number of particles in the ectoderm diminishes as the gastric pouches become developed. Ectodermal nourishment may also be observed in the ovarian ova of animals whose generative cells are ectodermal, such as Tubularia and Hydra. Wandering mesoderm cells perform intracellular ingestion and digestion not only in sponges, but in the larval forms of certain Echinoderms, where they digest the cellular débris of the disappearing organs, and phenomena of this kind are so constant among Echinoderms that they may be regarded as normal and necessary events in the life of their larvæ, where they play the same part as the osteoclasts of vertebrate bone. The author thinks that the same resorbent function is to be noticed in the larvæ of Ascidians, and may perhaps be found in Arthropods. Metschnikoff has extended to Aurelia aurita, Schneider's observation of the resorption of generative products by amoeboid cells in the Hirudinea. In attempting to define the extent of this property of intracellular digestion, the author has studied the transparent and hardy Bipinnaria asterigera, and Phyllirhoe bucephalum; giant cells appeared round foreign bodies injected beneath the epidermis, whether they were merely particles of carmine or a drop of human blood. In *Arbeit. Zool.-Zoot. Inst. Würzburg, v. (1883) pp. 141-69 (2 pls.). other words, in most though not in all cases we find that when mesoderm cells are confronted with a large mass of food-material which they cannot devour singly, they fuse into a plasmodium, which eats up the whole available food. Not only blood but milk also is absorbed by mesodermal cells, and further these cells appear to have some means of distinguishing between desirable and undesirable substances. The property of ingestion is not confined to the lower forms, for Koch has observed both Bacillus anthracis and the bacillus of septicemia inclosed in white blood-corpuscles; the power of intracellular ingestion is, in other terms, used as a protection against harmful bodies which come to an organism from without. Septic organisms, then, must be a very old source of trouble, and some arrangements, such as the peculiar test of Ascidians or the nematocalyces of Plumularia, may owe their origin to their influence. Metschnikoff hopes that the advances lately made by pathology will benefit zoology, which, in its turn, will help to form a comparative pathology based on the doctrine of evolution. In a further communication* E. Metschnikoff discusses the ancestral history of the inflammatory process. He has lately applied the name of phagocytes to certain cells which have the power of ingesting and sometimes of absorbing food-particles; the intracellular absorption which goes on in the mesoderm of the Invertebrata, is found to obtain also in that of the Vertebrata. The tail of the Batrachia, during the early stages of its absorption, contains a number of cells, which, when left undisturbed, throw out fine radiating pseudopodia; these contained remnants of nerve-fibres and muscle-cells: phagocytes, then, play as important a part in the metamorphosis of Batrachians as of Echinoderms; and pathologists have afforded evidence of their agency in the so-called active degeneration of muscles and nerves. A frog fed with bacteria was soon found to have them especially abundant in the phagocytes of the spleen, which, therefore, is probably a prophylactic organ, analogous in function to the nematocalyces of Plumularia. The author has tested in a Triton the theory he holds as to the phenomena of inflammation in invertebrates being primitively nothing more than a collection of phagocytes assembled to devour the exciting object; he touched a point of the tail of a Triton with a small piece of nitrate of silver, and then washed it with salt solution. Branched connective-tissue-cells collect round the inflamed spot, and cat up blood-corpuscles, carmine granules, and particles of pigment. In the frog there is evidently an active wandering of the white blood-corpuscles. When a fully gorged phagocyte dies, it is immediately devoured by another. Inflammation then is not, as is ordinarily supposed, due primarily to a morbid condition of the walls of the blood-vessels; it is a struggle between phagocyte and septic material, and it is in vertebrates alone that the vascular system, owing to the insufficient number of extra-vascular phagocytes, takes part in the struggle. The active passage of the white and the passive exit of the red blood-corpuscles is rendered possible by the changes in the cells of the walls of the capillaries due to the irritation set up by the poison. Mollusca. Gustatory Bulbs of Molluscs.*-W. Flemming discusses the nature of the organs found on the tentacles of various molluscs which have the structure of gustatory bulbs. On the tentacles and marginal tactile organs of Trochus cinerarius the author has observed closely packed long papillæ, which are also scattered over the edge of the mantle and the head. In a fresh papilla there is an indistinct internal longitudinal striation which, on isolation, is seen to correspond to a central bundle of long cells; these cells are provided with fine short cilia, of which there are several on each cell; by far the largest part of the papilla is composed of epithelial cells. Gold-staining reveals the presence of primary nerves giving off a large number of lateral branches, sufficient apparently to supply each papilla with a terminal nerve. Structures of a similar character are to be found among the Lamellibranchiata. The organs just described may, it is clear, be fairly compared with those which F. E. Schulze has spoken of as the gustatory organs of tadpoles, which are, likewise, freely projecting epithelial papillæ ; nor do these, except in their position, differ essentially from the gustatory bulbs of mammals; the only important difference between the organs of the Mollusca and the Vertebrata is to be found in the fact that in the former the end-hairs of the central sensory cells project freely, while in the latter they still lie within the bulb; as, however, the ends of the hairs are, even in the latter case, in direct contact with the surrounding fluid, the difference is not one of much importance. Although it is not certain that the end-organs described as existing in certain Mollusca have a gustatory function, yet Haller's suggestion to this effect has much to recommend it. From the point of view of developmental doctrines it is certainly of interest to observe that in some forms there are specific sensory organs at the very points where in most, and even in the most closely allied forms, there are only scattered ciliated cells. It is for the zoologist to extend the area of these observations. Morphology of the Renal Organs and Colom of Cephalopoda.+ -C. Grobben first deals with Sepia officinalis, then with Eledone moschata, and next treats of Nautilus in a comparative way. As is well known, the last-named cephalopod has four instead of two renal sacs, but it is not yet certain whether this arrangement is the more primitive or not. Those who regard Nautilus as phylogenetically the more ancient form would be naturally inclined towards the former view; against this, however, there are certain facts to which Ihering has already directed attention. That anatomist has pointed out that the anterior renal sac has no connection with the coelom, and that, therefore, it is a structure which has not been reduced in the other or dibranchiate Cephalopoda; Grobben now suggests that it is an offshoot of the primitively simple, and in Nautilus posteriorly placed, kidney; * Arch. f. Mikr. Anat., xxiii. (1884) pp. 141–7 (1 pl.). † Arbeit. Zool. Inst. Wien, v. (1883) pp. 179-252 (3 pls.). |