Female organs.—These consist of two ovaries, two oviducts or fallopian tubes, two uteri, two vagina, an uro-genital canal, a clitoris, mam mary organs, and marsupial pouch.
The ovaries are small and simple in the uniparous Kangaroos; tuberculate and rela tively larger in the multiparous Opossums ; but the largest size and most complicated form of these essential organs which I have met with in the Marsupial order were pre sented by the Wombat (fig. 137). The ovaria are represented of their natural size in fig. 138, a a, in the great Kangaroo, where they present an oval form and a smooth unbroken exterior, except after impregnation, when a large corpus luteum projects from the surface, as at a'. The ovaria are not inclosed by a cap sular duplication of the peritoneum, but are lodged within the expanded orifice of the ovi duct, or 'pavilion,' near the upper or anterior extremities of its two principal lobes or pro cesses. These are of considerable extent, and their internal surface, which is highly vas cular, is beset with rugw and papilla. In the Dasyures and Petaurists the ovaries are elliptical, subcompressed, and smooth. In the Opossum the ovarium consists of a lax stroma remarkable for the number of ovisacs imbedded in it, the largest of which are the most super ficial, and give rise to the tubercular projections on the surface of the ovary.
In the Wombat (fig. 137) each ovary, be sides being lodged in the pavilion, as in the Kangaroo, is inclosed with the pavilion in a peritoneal capsule. In the unimpregnated female examined by me, the ovaries were six times as large as in the Kangaroo, and pre sented a well-marked botryoidai form, resem bling the ovarium of the bird. Numerous ovi sacs in different stages of growth projected from the surface, the largest presenting a diameter of eight lines (fig. 137, a); the structure of these ovisacs, the character of the stroma in which they are imbedded, and the dense albugineous tunic by which they are inclosed, bespeak the strictly mammalian type of the ovaria of the Phascolo mys as of every other genus of Marsupial; but the affinity of the Wombat to the Rodent order, in many species of which the ovaria are tu berculate, is again manifested in this part of its structure. The expanded orifices of the fallopian tubes present a greater development than in the Kangaroo, and are still more re markable for the number, size, and variety of the fimbriated processes and folds which aug ment the internal vascular surface of the pavi lion. In both the Wombat and Kangaroo the
lining membrane of the contracted portion of the oviduct is similarly complicated by minute and delicate reticular plications and processes. The oviducts are shorter and less sinuous in their course in the uniparous Kangaroo, fig. 138, I), than in the multiparous Opossums ( b, fig. 139).
In the above described essential parts of the female generative apparatus the mammalian type of structure is closely adhered to ; the de viations most characteristic of the implacental group begin to manifest themselves in the re maining parts, and here under so irregular and complicated a form as to require a brief review of the analogous structures in other groups of animals for their intelligibility.
The variations of structure which the female generative organs present in the oviparous classes of Vertebrate are fewer and of less de gree than those observable in the different orders and genera of the Mammalia. The most pre vailing characteristic of the oviparous type of the female generative organs is the absence of union in the mesial plane of the lateral efferent tubes, which consequently continue separate to their terminations in the excretory outlet.
In Birds the genital apparatus is characterised by the higher, and, in the female, as Far as function is concerned, exclusive development of the left moiety ; and the uniformity in the condition of the excluded ovum in this class corresponds with the sameness which prevails in the structure of the organs concerned in its production.
In Reptiles the ovaries and efferent parts of the genital system are equally developed, or nearly so, on both sides. But although a con siderable uniformity of structure is found to pre vail in this system throughout the different orders of the class, the widest difference obtains both in the place of development of the ovum and the condition in which it quits its mother. No one, e. g., could have predicated from a comparison of the structure of the ovaries and oviducts in poisonous and innocuous Serpents that any difference existed in the structure and development of the ovum, much less that the for mer were ovo-viviparousbut the latter oviparous; or, from a comparison of the same organs in Lacerta crocea and Lacerta agilis, that a like difference should exist in the generative eco nomy of species so nearly allied as for a long time to have been confounded together by naturalists.