plex horns result from the direction of the main axis or line of greatest increase in the wapiti, or American elk, as well as in the stag of Europe, this is along the protoceres throughout, while in the common Virginian and long-tailed deer it is procurrent subspirally into the tritoceres. The Elaphure of China is anomalous in the excessive development of the deuteroceres, or homologues of the brow-antlers of the wapiti and stag, and the inverse reduction of the other elements.

The Placenta of Prosimians.

One of the most interesting groups of mammals is that of the Prosimians, comprising the lemurs, the Tarsius, and the aye-aye, most of which are found in the great island of Madagascar. The special interest arises from the fact that, in many points of structure, they approach the apes and man more than does any other form. On account of the possession of their many common characters, the two groups of Apes and Prosimians have been, by most writers, combined under the ordinal designation of Primates, although quite a number of prominent naturalists have urged that the two should be differentiated as distinct orders. The question was reopened several years ago by Mr. A. Milne-Edwards, who examined the placentation of several species of Prosimians, and found that it differed widely from that of the Apes. The placentation of species of the group has still more thoroughly been investigated, during the past year, by Professor W. Turner, of Edinburgh, who has in part confirmed and amplified the observations of Mr. Milne-Edwards. His examination extended to three species-viz., Lemur rufipes, Propithecus diadema, and Indris brevicaudata.

A number of prominent zoologists have combined the orders of placental mammals under groups distinguished by the placenta. In one type, as in Man, the uterus develops a decidua, and the placenta is discoidal; such are Man and the Apes, the Bats, the Insectivores, and the Rodents. In others the placenta is deciduate and zonary, as in the Carnivores and the Proboscideans; and in a third the uterus develops no decidua whatever, as in the Ungulates and Cetaceans. Until the discovery of the placentation of the Lemuroids, it had been very naturally assumed that they possessed a discoidal deciduous placenta like the apes. It is

now satisfactorily proved, however, that no decidua is developed, and the placenta exhibits a modification of a zonary form. "Both in form and structure," says Mr. Turner, "the placenta in the lemurs is without doubt a diffused placenta." The question naturally arises, What is the value of the placental characteristics of the Prosimians? Are those animals related most to the other forms developing a decidua, or to the Primates, with which they have been hitherto generally associated, or at least approximated to? Professor Turner has quite judiciously treated this question; and has contended that in spite of the placental characters, the Prosimians are closely related to the typical or ape-like Primates, with which they agree, or most resemble in a number of osteological and cerebral characters. He urges, however, that the two groups are entitled to ordinal value; the apes, with man, belonging to one (Primates), and the lemurs and related types to the other (Prosimians). He urges, with considerable force, that the non-deciduate "diffused placenta has the most simple mode of structure, and that the distribution of the villi over the surface of the chorion presents a closer approximation to the primary embryonic arrangement; while the discoid placenta exhibits the greatest departure from the diffused villous chorion of the early embryo." It is therefore probable, he thinks, that the mammals with discoid deciduate placenta have diverged from those characterized by a non-deciduate one. He has shown, too, that the line of demarcation between the non-deciduate and deciduate placentiferous mammals is not so abrupt as has usually been supposed, but is graded over by an intermediate arrangement "the passage from the diffused placenta, in which no maternal tissue deciduates during parturition, to those deciduate placentæ in which both the epithelial and subepithelial vascular tissue of the uterine mucosa are shed being effected through the cotyledonary placenta, in which the epithelial lining of the maternal cotyledons separates along with the foetal villi." There is, besides, considerable variation in the relative proportions of the tissues.

INVERTEBRATES.

Protozoans, Sponges, and Worms.

"Studies among Amabæ" is the subject of an article in the Popular Science Review for July, by Professor P. M. Duncan, who describes the habits and figures of some of the forms of these protozoans. Of the twenty or more species described by German and English observers, Duncan believes that there are but two truly specific forms, Amaba villosa and Amoeba princeps.

Dr. Leidy has observed a species of infusorian, probably Chilomonas, existing in immense numbers on the sandy beach of Cape May, where they formed a thin yellowish-green film, coloring the surface of the sand.

An important work on the development of the egg has been published by O. Bütschli, who is well known by his studies on the Infusoria and the lower worms, especially the Rotifera and the Nematode worms. As regards the process of conjugation among the Infusoria, Bütschli, according to a review of his work in Nature, thinks that it is merely a rejuvenescence of the creatures which undergo it, enabling them to become "the stem ancestors of a series of generations which propagate by fission." This is contrary to the view of Balbiani, Stein, and others, who maintain that the act of conjugation so well known among the Paramecia, Vorticellæ, etc., is the precursor of a sexual mode of generation. The reviewers, Messrs. Dallinger and Drysdale, disbelieve in Bütschli's theory, and suggest that "what he calls rejuvenescence is one of the many modes by which rapidity of fissiparous multiplication is in some organisms aided, and the necessity for the true act of fertilization is made less frequent."

The foraminiferous forms shall we say varieties or species?—of Barbadoes have been studied by Van den Broeck. His material was received from the West Indies, having been collected by the late Professor Agassiz. He concludes, with all others who have studied these exceedingly variable forms, "that the terms genus, species, variety, have a very different and broader acceptation than we usually suppose."

A severe critique on Dr. W. B. Carpenter's views regarding certain groups of Foraminifera, by Dr. G. C. Wallich,

appears in the Annals and Magazine of Natural History for February.

The fresh-water Rhizopods, a favorite subject of inquiry, have been studied with great care by Hertwig, Lesser, and Bütschli. An abstract of their works has been given by Mr. Archer in the Quarterly Journal of Microscopical Science, the third part appearing in the January number.

Barrois finds that the sponges of the different groups studied by him present the same essential processes of development, but that these stages appear in a different order, and more or less modified by different circumstances, in the different groups. This general mode of development, or primitive cycle, does not seem to him to be a gastrula fixed like a hydra, and of which the inner layer is ramified into a gastro-vascular system, as Haeckel supposes, but a compact mass composed of two layers, the exterior representing the exoderm, the interior the union of an internal and middle leaf. From the middle layer arise the spicules. The oval gastrula becomes fixed by its posterior end, and then becomes flattened and irregular in form; cavities then appear in the endoderm, or innermost layer, which are lined with the peculiar ciliated cells found in sponges; and the oscules then appear, by which water enters and bathes the cavities within. These observations of M. Barrois do not seem to sustain Haeckel's views as to the relationship of the sponges to the polypes, with which he unites them.

While Mr. Carter continues, in the Annals and Magazine of Natural History, his papers on sponges, a memoir by Professor Haeckel forms the second number of his "Studies on the Gastræa Theory." It contains, however, besides considerable theoretical matter, many new facts regarding certain simple. sponges called Haliphysema and Gastrophysema. They are so simple in organization as to bear considerable resemblance to the gastrula form of sponges, which, it may be remembered, consists of a two-layered hollow sac. It is illustrated by six well-drawn plates.

The commercial sponges of our southern coast have been described and figured by Professor Hyatt in a lengthy memoir published by the Boston Society of Natural History, in which he describes the mode of fishing for them, as well as the manner in which they are prepared for the market.

Hyatt also discusses the influence of the nature of the seabottom and the temperature of the water on variations of forms and their distribution. He claims that these animals are directly modified by changes in the physical surroundings, and he cannot imagine the intervention of natural selection, since "the uniform action of a given temperature, depth, amount of sediment, sheltered locality, etc., have a corresponding uniformity in results, and are sufficient in themselves to account for the general modifications described."

A number of new Caribbean sponges are described in the Annals and Magazine of Natural History by Thomas Higgin. Certain minute parasitic worm-like organisms, called Dicyema and Dicyemella, which live in the liquid bathing the spongy bodies (perhaps renal organs) of cuttle-fishes, have been studied in all their phases of development by a Belgian naturalist, E. Van Beneden, who concludes that they form the type of a new sub-kingdom of animals, which he calls Mesozoa.

It appears that tape-worms may occur abundantly in the intestines of rabbits, as stated by Mr. G. J. Romanes in Nature. This is an unexpected fact, since the rabbit is purely an herbivorous animal. The fact is explained by Mr. R. D. Turner in a letter to Nature (February 15), who says: "I would suggest that the tape-worm referred to by Mr. G. J. Romanes is like the Bothriocephalus of man, perhaps a species of the same genus. This is not supposed to have a cystic state, but to be developed from a ciliated embryo taken into the system in raw or badly cooked vegetables which have been watered by sewage from cesspools, in which the eggs will remain alive for months. In the same way the eggs of the rabbit's tape-worm probably remain in the animal's droppings till set free in rain as ciliated embryos. As the rabbit feeds on the vegetation watered by such rain, there is no difficulty in understanding how the embryos would reach his alimentary canal."

Some of the fluke-worms (Distoma, etc.) of Scandinavia are described and figured by Olsson in the Transactions of the Swedish Academy.

The classification of the lower worms, especially the flat worms, forms the subject of two elaborate papers by Mr.