Visceral Nervous System of Periplaneta orientalis.* - M. Köstler, after a detailed notice of the work of preceding anatomists, commences with the unpaired visceral nervous system, which can be best studied by the method of sections: he finds in it (1) a frontal ganglion; (2) the nerve on the oesophagus and crop; (3) the large triangular ganglion on the crop; and (4) the two nerves thence given off with their accessory ganglia. In the first of these we find the socalled central dotted substance, and it is surrounded by a layer of ganglionic cells; these last are traversed by a special supporting substance such as Dietl has found in the cerebrum; from the neurilemma surrounding the ganglion fine connective cords pass off in all directions towards the central mass; the ganglionic spheres are always of a larger size than they ever are in the brain; they are rarely pyriform in shape, and never have any investment; the protoplasm is collected into nuclear masses of some size, and a concentric disposition of the layers is easily seen. The spheres are almost always unipolar, bipolar cells being very rare, and multipolar only once observed, and this may have been due to an optic illusion.

The unpaired visceral nerve has exactly the same structure as that of the commissures of the ventral ganglionic chain, and the grey granular fibres call to mind the sympathetics of the Vertebrata. The large ganglion on the crop has a very similar constitution to that of the frontal ganglion.

With this unpaired system there is correlated a paired visceral system of nerves; the development of one standing in opposition to that of the other. It consists of a number of small oval ganglia which lie on either side of the median unpaired nerves, and are connected with the brain; they have the usual fibrillar structure, and have a few elongated ganglionic nuclear masses imbedded in them. Their chief function appears to be to innervate the large salivary glands.

The true sympathetic nerve can be seen by removing the ventral ganglionic chain, and treating it for a short time with the vapour of osmic acid; two sets of nerves will then be distinguished, for the ventral chain will be found to have taken a distinctly dark coloration, while between the longitudinal commissures much lighter nerves are to be seen. Almost in the middle of every such commissure, alternating now to the right, now to the left, there will be seen passing off a fine nerve; at the level of the ventral ganglia this nerve divides into two parts, each of which swells out into a small spindle-shaped ganglion, and then passes into the lateral nerve given off from the ganglion, its own pale fibres mixing with the cerebro-spinal, and taking the same course as the peripheral nerves.

The author thinks that when we make a general comparison between the visceral nervous system of Arthropods and of Vertebrates we can have no doubt that the true sympathetic of the one is that also of the other. Its relation to the ventral chain is reversed indeed. The unpaired nerve is cerebral and corresponds to the vagus, and its grade of development is dependent on that of its possessor, so that in

*Zeitschr. f. Wiss. Zool., xxxix. (1883) pp. 572-95 (1 pl.).

the larval stage, when the organism needs more food, it is larger than it is later on. Differences are to be seen in the disposition of the appended ganglia, but the great ganglion frontale is perhaps a separated portion of the cerebrum, which owes its special position to the development of the anterior portion of the digestive tract.

Pulsating Organs in the Legs of Hemiptera. - Conflicting opinions have been held regarding the pulsating organs that have from time to time been observed in the legs of certain Hemiptera. W. A. Locy records some observations which enable him to say that these organs are distinct from the muscular system of the legs, and that they influence circulation. Their automaticity was also observed. Specimens for examination were chosen with reference to the transparency of their legs, as it is upon this point the success of observation depends. Both larval and adult forms of the genera studied were used, but the best results were uniformly obtained with the larval forms, for the above reason. In some cases special methods were necessary to render the legs transparent enough for observation. For this purpose the integument of the legs was scraped very thin. The organs can be demonstrated in this manner, even in the thick legs of the adult Belostomæ. They are most easily seen in the legs of Notonecta and Corixa, but are not so large and pronounced as in the legs of the Nepida. In the more transparent individuals not only are the organs readily seen, but the circulation of the blood can be watched with a power high enough to bring out the corpuscles.

7. Arachnida.

Vitelline Nucleus of Araneina.†—A. Sabatier adopted the following method in his investigation into the structure of the ova of spiders. The animals were opened while alive in a few drops of alcohol, so as to harden and fix the eggs at once; sometimes, though rarely, osmic, picric, or acetic acid was used. The eggs were stained with Beale's carmine or picrocarminate of ammonia; after washing, they were placed in phenicated glycerine.

The vitelline nucleus was observed in all the Araneids examined; its presence is ordinarily marked by its affinity for the colouring matters which are taken up by the yolk. Sometimes, indeed, its presence is only revealed by the existence on its surface of refractive granules which mark out its spherical form. In Tegenaria agrestis it is often very distinct.

This nucleus arises in the neighbourhood of, or even in contact with the germinal vesicle under the form of a mass, which, speaking generally, differs from the yolk by being more finely and evenly granular, by a greater affinity for colouring matters, and sometimes by higher refractive power. It has a massive and not vesicular structure; when it does not undergo stratification it consists of a spherical mass of protoplasm, without membrane or nucleolus, and with no chromatin-plexus, though it probably has some chromatin * Amer. Natural., xviii. (1884) pp. 13-9 (1 pl.).

+ Comptes Rendus, xcvii. (1883) pp. 1570-2.

diffused through it. It is possible, but the question must still remain an open one, that it is merely a massive nucleus. It gradually separates itself from the neighbourhood of the germinal vesicle, and passes to the periphery of the yolk; it becomes more granular, and undergoes disintegration; its elements, divided into small globules, independent of one another, are in parts absorbed by the yolk, or gradually become merged in the superficial granular protoplasm. The vitelline nucleus may, therefore, be looked upon as a centrifugal element, which tends to eliminate itself or to lose its "autonomy." Sabatier regards it as an element of male polarity, which is destroyed as such to accentuate and complete the sexuality of the female cell.

Restoration of Limbs in Tarantula.*-H. C. McCook recently exhibited a tarantula which had been kept in confinement nearly a year, fed during winter on raw beef and in summer on grasshoppers. In the spring it cast its skin by a laborious process, in the course of which it lost one foot and two entire legs. Last summer again, during the latter part of August, the animal moulted; the moult being a perfect cast of the large spider-skin, spines, claws, the most delicate hairs all showing, and their corresponding originals appearing bright and clean upon the spider. The moulting occurred during Dr. McCook's absence, but was just finished when he returned. When the cast-off skin was removed it showed, as might be supposed, the dissevered members to be lacking. But on looking at the spider itself, it was seen that new limbs had appeared, perfect in shape but somewhat smaller than the corresponding ones on the opposite side of the body. The dissevered foot was also restored. The loss of the opportunity to see the manner in which the legs were restored during moult was greatly regretted; but we have some clue from the careful and interesting studies of Mr. Blackwall. Several spiders whose members had been previously amputated, were killed and dissected immediately before moulting. In one of these the leg which was reproduced was found to have its tarsal and metatarsal joints folded in the undetached half of the integument of the old tibia. Another like experiment was made with an example of Tegenaria civilis. The reproduced leg was found complete in its organization, although an inch in length, and was curiously folded in the integument of the old coxa, which measured only 1/24 in. in length. Dr. McCook's tarantula had lost both legs close up to the coxæ, and in the moult the hard skin formed upon the amputated trunks was wholly unbroken, showing that the skin had been cast before the new leg appeared. We risk nothing in inferring that, as in the case of Blackwall's Tegenaria, the rudimentary legs were folded up within the coxa, and appeared at once after the moulting, rapidly filling out in a manner somewhat analogous to the expansion of the wings in insects after emerging.

Morphology of Plumicolous Sarcoptide.†-E. L. Trouessart and P. Mégnin have a second note on this subject, in which they

Proc. Acad. Nat. Sci. Philad., 1883, pp. 196-7. + Comptes Rendus, xcvii. (1883) pp. 1500-2.

point out that, though most plumicolous Sarcoptids are oviparous, some are viviparous (e. g. Fryana); the covering of the egg is sometimes tubercular and sculptured, and in Analges fuscus has a double row of cells, comparable to the ring of certain sporangia, and forming an organ of dehiscence. The dorsal tegumentary plates are not always granular, as in the species studied by Robin; they are often perforated or reticulated. The nymphs are sometimes found under two forms, which differ in size. The curious red-coloured vesicles which are found on the flanks of a species of Pterolichus may be regarded as secondary sexual organs; the female has two, the male one pair. When highly magnified they have the appearance of a flattened uniform plate, formed of a large number of tubes which open into an excretory canal, the orifice of which is lateral or posterior. The red colour is due to a liquid which fills the tubules. They appear to be modified segmental organs, but their function is still unknown.

8. Crustacea.

Sexual Characters of Limulus.*-B. F. Koons has been puzzled by the fact that no cast-off shells of Limulus bearing the characteristic modified claw of the male have been found; he now sees that this is to be explained by the young male having the claws of the second pair of appendages similar to those of the female; as no large exuviæ have been found it is probable that the fully grown Limulus does not shed his integument. Howsoever young specimens may be, the sexes are to be distinguished by the transverse slits of the oviducts, and the papillæ with terminal circular orifices in the male. Females are larger than males, and the carapace of large specimens is overgrown with algæ, and appears rusty and aged, while those of smaller examples are bright and clean, pointing to their being frequently shed; indeed the covering appears to be shed several times during the first year. While the entire length of the exuvia may be only 4.0 mm. the escaped young measure 7.1 mm.: an exuvia of 7.0 mm. has a naked young of 10.7 mm., while when the shed integument is 29 mm. the escaped young have been found to be as much as 40 mm. in length. Corresponding differences obtain in the different parts of the animal.

Evidence of a Protozoea Stage in Crab Development.t-There is great interest attached to speculations as to the probable ancestry of the Decapods, owing to the value which the conclusions have in enabling us to interpret palæontological facts. There have been quite a number of theories advanced as to the original stem from which the Decapods have been derived, two of which claim especial attention. One is the theory of Müller, who finds such a stem form in the zoea. Another, suggested by Claus, or in a different form by Brooks, considers the protozoea as the ancestral stem. It is of great importance in understanding the Crustacea to decide between these two views, inasmuch as by the first view Crustacea are supposed to have descended from a form without a thorax, while according to the

* Amer. Nat., xvii. (1883) pp. 1297-9.

† Johns-Hopkins Univ. Circulars, iii. (1884) p. 41.

second, the thorax was present in the original Decapod stem. Some work done by H. W. Conn, during the last summer, upon the larval cuticle of crabs, indicates conclusively (it is claimed) that the latter view is the correct one, or that at least Fritz Müller's view is incorrect. The larval skin, particularly the telson of a large number of crab zoeas, was studied with the following results.

The larval skin is not in different crabs alike, nor is it in any case exactly similar to the inclosed zoea. There is always an indication more or less complete, of some previously existing stage. There has been shown in the various forms studied a gradation from the larval skin, with little difference from the zoea inclosed, to a larval skin which is utterly unlike the zoea, but which possesses a forked tail with fourteen long feathered spines. This gradation is complete, and a study of the different embryonic telsons shows that all have been derived from the form shown by Panopeus, which has a forked tail with fourteen spines. Now, such a larval skin is to be considered simply as the cast-off skin of some stage immediately preceding the zoea. It has been shown by Paul Meyer that the study of the skin of Macroura leads to a similar result, that a forked tail with fourteen spines is also seen in the early history of this group. If, therefore, a form can be found which shows these peculiarities, we have reason for accepting it as the stem form of the higher Crustacea. Now a study of the different protozoea forms which occur in the ontogeny of various Macroura shows that we have in this form a stage which fulfils the conditions. It has the forked tail with fourteen spines and has large swimming antennæ, another peculiar characteristic of the crab larval cuticle. If the various larval skins of crabs and Macroura be compared with each other, it will be seen that they are all to be considered as modifications of a tail much like that present in the larval skin of Panopeus; and if this tail be compared with the protozoea tail of Peneus, the likeness will be seen to be very striking. We have, therefore, in the comparative study of the larval cuticle of crabs, good reason for accepting as the stem form of the Decapods a form which had resemblance to a protozoea.

Gastric Mill of Decapods.-F. Albert has studied the digestive or gastric mill of Decapod Crustacea in great detail, in the descriptions of which he makes use of the nomenclature proposed by Nauck.

The simplest arrangements of the hard parts in the gastric wall of Decapoda are to be found in the prawn-like forms, where, however, there is not so much a primitive type, as well-developed characteristics which it is sometimes difficult to bring into association with the majority of forms, owing to the absence of certain intermediate links. Among the Natantia we find, on the one side, forms in which the cardiac apparatus, and others in which the pyloric part of the organ is best developed. In both cases the same plan has been followed; two paired and lateral teeth have entered into a physiological connection with an unpaired median process. At the end of one line of

* Zeitschr. f. Wiss. Zool., xxxix. (1883) pp. 444-536 (3 pls.).