development we find a superomedian tooth with superolateral structures, and in the other the tooth of the inferomedian pouch is well developed, with its tooth-like lateral processes. The Alpheinæ, Palæmoninæ, Crangonine, and Gnathophyllinæ are in common characterized by the fact that the inferomedian and inferolateral regions of the cardiac and pyloric portions are alone provided with hard structures of characteristic form; the inferomedian cardiac process evidently consists of three distinctly differentiated longitudinal portions; of these the median one has few or no setæ, while the lateral portions have short setæ, of various forms and arranged in groups, which look towards the middle line; with this are placed longer seta which form a continuous fringe, and, when the gastric musculature is well developed, this fringe is provided with special muscles. The effect of this arrangement is to confine the food-particles to the median line, and to drive them along it into the thoracic region of the stomach. Bearing this in mind, we can understand that the loss of the peristaltic action of the stomach is due to the reduction of the cardiac process and the great development of the pyloric superomedian process.

The author concludes from his elaborate survey that the hard structures of the stomach of the higher Crustacea are most important aids in the classification of these forms; and his own results coincide with those arrived at by v. Boas. The Natantia form the lowest groups, and the Eucyphotes may be defined as Decapods without a cardiac dorsal mill, and the Penæidæ as Decapods provided with one. The Atyinæ appear at present to be isolated forms, but a connecting link may perhaps be found in Troglocaris. The Sergestidæ are to be placed with the Penæidæ, as are also the Cerataspis forms, which are often associated with Schizopoda. The well-defined group of the Homarida may be divided into the Homarine and Astacinæ, as Boas has suggested. The Anomala (in the sense of De Haan) do not form a definitely separated group.

The type of gastric mill found in the Decapoda may be continued into the Squillidæ, Myside, and Cumacea, where almost all the corresponding parts are to be found. The median inferomedian pyloric process forms a crest-like longitudinal invagination, and passes through very interesting gradations; in Diastylis it has one, in Mysis two, in Gammarus three, and in the higher Malacostraca a number of fringes of longitudinally-set setæ; indeed, the number increases as the form possessing them stands higher in a systematic classification.

Spermatogenesis in Hedriophthalmate Crustacea.*—G. Herrmann finds that the spermatogenesis of hedriophthalmate is effected on a different plan to that of the podophthalmate Crustacea. The male cells are of large size, and, soon, come to have a number of nucleoli, around which the nucleus seems to undergo segmentation. This is followed by a stage in which there is a group of smaller nuclei, irregular in form, more or less definitely arranged round the periphery of the sperm-cell (" ovule "). This latter divides into equal parts, and soon small cell-elements, with a nucleus, but without a

* Comptes Rendus, xcvii. (1883) pp. 1009–12.

nucleolus, appear. The cephalic nodule is now formed, as a small cup-shaped disk, attached to the surface of the nucleus. As in the Vertebrata, the spermatic filaments are developed at the expense of the spermatoblasts, but the cephalic nodule, which in all other animals has an important function, is here only secondary. A little later the spermatozoid is found to consist of three segments—a cephalic, which incloses the spermatoblast and its nucleus, a median segment which is scarcely visible, and a caudal segment or filament. Later on, the nucleus becomes ovoid in shape, with its long axis in an antero-posterior direction; after it has elongated, its hinder extremity separates from the cell-body of the spermatoblast, and it finally leaves the cell. The flagellum becomes of proportionately great size. Eighty to one hundred spermatic filaments are united into bundles, which are placed in the grooves of the epithelial cells which line the walls of the tubes. Isolated spermatozoa have only been found in the oviducts of the female.

With the exception of its cephalic nodule, the spermatozoon of a hedriophthalmate crustacean has very much the same history as that of the Selachians, and it is to be noted that these spermatozoa exhibit a more complete type than those of the Podophthalmata, inasmuch as in the latter they may be reduced to the single cephalic segment.

Vermes.

Structure and Division of Ctenodrilus monostylos.-M. Zeppelin gives a full account of this new species of marine annelid. It is about 3 or 4 mm. long, and 0.2 wide, and consists of 20-25 wellmarked segments, and is of a yellowish-brown colour. It is remarkable for the possession of a protrusible proboscis which is quite independent of the enteric canal. The only pair of segmental organs is found in the head. The buccal cleft is ciliated, as are also the œsophagus and the rectum. All the segments but the last have setigerous sacs, with two or three setæ apiece. They move very slowly. Sexual reproduction has not yet been observed, but only transverse division. The habitat of the worm is not known, the specimens examined having been found in an aquarium at Freiburg.

The cuticle is thin and homogeneous, the hypoderm thick and made up of polygonal cells with scattered pigment-spots. The musculature is of a very primitive character, the dermomuscular tube consisting of a simple layer of longitudinal fibres which extend uninterruptedly to the end of the body; in this point C. monostylos has a striking resemblance to Polygordius. Although metamerism is very distinctly expressed externally, it is not so well marked internally as in most forms, the enteron, for example, not being constricted by the dissepiments. The setæ are very regularly distributed over the body, and are either thin and sharp, or stronger and shorter; the two last metameres which are not so well differentiated as the rest, have, as a rule, no setæ. The enteric canal is a little longer than the

* Zeitschr. f. Wiss. Zool., xxxix. (1883) pp. 615-52 (2 pls.).

body, and is for a great part ciliated; the ciliation resembling exactly that of Eolosoma quaternarium.

The blood-vascular system exhibits a very low degree of development, consisting of a dorsal and ventral trunk, which extends through the whole length of the animal; the former gives rise, in the first segment, to a short transverse trunk, from which arise two lateral trunks. The blood is yellow and non-corpusculated; the walls of the vessels are formed by a fine structureless membrane in which nuclei are imbedded. Distinct pulsations could not be detected, though there was a regular current. A structure, comparable to the solid cord of cells in the interior of the dorsal vessel, described by von Kennel in Ctenodrilus pardalis, is here also present; both these may be compared with the darkly-coloured organ found by Claparède in Cirratulus, Terebella, and others.

The head is made up of the cephalic lobes and oral segment, and is distinguished from the metameres which succeed it by its relatively greater length and the possession of the very characteristic proboscis, of the tentacle, and of the segmental organs. The cœlom, as in C. pardalis, extends into the cephalic lobes. The whole of the ventral surface of the head is ciliated, and these cilia serve to drive currents of food to the mouth of the worm. The author regards the head as essentially different from all the succeeding segments. The proboscis lies beneath the mouth, and consists of a solid, muscular, broad plate; it opens into a chamber common to it and the mouth and has apparently the function of a locomotor organ.

The resemblances to Polygordius which this new form exhibits are emphasized by the possession of a single tentacular organ, the fellow of which seems to have been lost in the course of time. It arises just below the proboscis, and is capable of doubling its length; owing to the possession of a special musculature, it can also become considerably diminished. It is distinguished from the tentacle of Polygordius by the absence of a diverticulum of the cœlom; it is marked externally by a ciliated groove, the cilia of which work towards the body; it appears to be not only a tactile organ, but also to bring food to the mouth. Individuals with two tentacles are not rarely seen.

Like C. pardalis, C. monostylos has only one pair of segmental organs, and these are placed in the head; they are coiled, finely granular tubes, and the cilia around the cœlomic orifice are very delicate. In the nervous system the new species considerably resembles the already-described species of the genus; the dorsal ganglion is placed in the cephalic lobes, and its central mass is dotted; the ganglionic cells are only indistinctly separated from the surrounding epithelial cells; the ventral cord is not provided with metamerically arranged ganglia, but forms a simple well-developed cord, which extends through the whole length of the body; in very thin sections indications of a fine median membrane were occasionally detected, but no peripheral nerves could be made out. The nervous system remains in the hypodermis. Cells of peculiar character, and apparently of mesodermal origin, are to be found floating in the coelom.

The author next describes the processes of division, which seem to be of a much more primitive character than in C. pardalis; all individuals which consist of twenty or more segments are capable of division; there are no preliminary phenomena of gemmation, no zone of gemmation as in C. pardalis, but only a slight constriction of the integument, which gradually becomes more and more pronounced; the two daughter forms are at first without any head or anus respectively, and it is only some time after the constriction that these organs begin to be formed. They may give off fragments of one to three segments which have neither head nor anus, and are no longer capable of division, or pieces of five or six segments which may again divide and give rise to fragments similar to those already mentioned. Lastly, the daughter form with the primary head is capable, after the production of a secondary anus, of giving off the terminal portion, but it is not known whether the other half of the parent form is capable of a similar action. After discussing the phenomena of division which he has observed, and comparing them with what is known in other forms, the author passes to the affinities and systematic position of Ctenodrilus. He regards it as a collective type" which stands near the point of union of the Oligochata and Polychaeta, but, as in the case of Polygordius, we can hardly, as yet, assign to it a definite and fixed position in the zoological system. While it has, no doubt, an alliance with the Polygordiidæ, it has some special affinities to the Oligochatous Naids, and other characters in which it as much resembles the Polychata as the Oligochata.

Manyunkia speciosa.*-Under this barbarous name, J. Leidy describes a new fresh-water annelid closely allied to Fabricia. The tube is composed of very fine particles, cylindrical, sometimes feebly annulated. The tubes are formed separately, or a few together, and they measure from 2 to 4 lines in length, and 1/5 to 1/4 of a line in width. The mature worm is 3 to 4 mm. long, and 1/4 mm. in breadth, and consists of twelve segments, including the head; it is of a translucent olivegreen colour; the head is surmounted by a pair of lateral "lophophores," which support the tentacles. The seventh segment is twice as long as any of the others, and has an abrupt expansion at the fore-part, which suggested the production of a head prior to the division of the worm; gemmation, however, has not been observed. The number of tentacles varies with the age of the worm, but there are generally eighteen on each "lophophore" in a mature specimen; they are ciliated, and in all respects bear a close resemblance to those of the Polyzoa; they have various functions, and may be as justly called tentacles as cirri. At their base are six or more brownish pigment-spots, which resemble but have not the constitution of eyes. The segments behind the head are provided with a fascicle of locomotive setæ, some of which are shorter than the rest; there are from four to ten in each fascicle. The sets have the form of a long straight rod, with a blade which terminates in a long filament; some of the posterior segments have

*Proc. Acad. Nat. Sci. Philad., 1883, pp. 204–12 (1 pl.); and see E. Potts, ibid., January 22, 1884.

also a fascicle of " podal hooks," which vary not only in corresponding segments of different individuals, but on either side of the segments of the same individual.

The intestinal canal is a simple median tube dilated in each segment; the mouth is unarmed, funnel-like, and capacious. There is a well-developed eye on the head at the side of the gullet, but there does not appear to be any trace of posterior terminal eyes, such as are found in Fabricia. The ova appear to be laid and hatched within the tube, so that the young are cared for by the parent till sufficiently developed to provide for themselves.

The paper concludes with some observations on the species of Fabricia, to which M. speciosa is most closely allied; the simple eyes were observed to vary in different individuals, and on the different sides of the same individual.

Parasitic Nematode of the Common Onion.*-J. Chatin describes an apparently new species of Tylenchus, which infests the bulb of the common onion. In its larval stage, it penetrates into and disorganizes the central tissue, converting the fibro-vascular bundles into a brownish pultaceous mass. Growth goes on and the sexual organs become matured; the fertilized ova give rise to claviform larvæ, which are able to escape owing to the destruction of the bulb; these, if the ground is moist enough, wander about on it, but if it is dry they remain quiescent until damp weather comes. They then enter a healthy onion, and the cycle recommences. If the nematoid enters an animal host it passes out with the fæces, and does not undergo in its intestine any further development, nor does it become encysted. On the whole it has a close resemblance to the Anguillula of wheat, but it is not so capable of resisting desiccation. The best remedy against it is to burn all the affected onions.

New Myzostomata.†-L. Graff gives an account of the new species of Myzostomata which were collected by Dr. P. H. Carpenter off the Crinoids of the 'Hassler' and 'Blake' expeditions; of the 22 species, 21 are new; of those 14 are peculiar to the American collections, while the others have been found elsewhere also. Postponing all details to his Challenger' Report, the author here merely describes the species, which may be divided into two groups: the members of the first of these are hermaphrodite, ectoparasitic, and produce no deformity on their host; all but one species are provided with suckers: in the second group the animals have the sexes separate, and live by pairs in cysts of their hosts; they have no suckers. The entoparasitic forms produce various abnormalities, merely widening the pinnulæ, or at the same time converting them into a spiral coil, or they produce pyriform outgrowths of the pinnules, or various kinds of cavities in the arms. Cysts are sometimes formed by calcareous deposits, which are found on the arms as well as on the disk.

Bucephalus and Gasterostomum.-H. E. Ziegler gives an account of these two parasites. After an historical review and an account of the * Comptes Rendus, xcvii. (1883) pp. 1503-5.

+ Bull. Mus. Comp. Zool., xi. (1883) pp. 125-33.

Zeitschr. f. Wiss. Zool., xxxix. (1883) pp. 537-71. (2 pls.).