MARSUPIALI A. 



313 



lateral and posterior part of the penis, until it 

 is inserted with the opposite muscle at the 

 base of the glans. 



In the Opossum and those Marsupials 

 which, having a bifid glans, enjoy, as it were, 

 a double coitus, there is a levator penis (f, J\ 

 fig. 136), which is not present in the Kangaroo. 

 Each portion of this muscle takes its origin 

 from the fascia covering the crus penis, con- 

 verges towards its fellow above the dorsum 

 penis, diminishing as it converges, and termi- 

 nates in a common tendon inserted into the 

 upper part of the base of the glans. 



There is another powerful muscle which, 

 though not immediately attached to the penis, 

 must exert, in all Marsupials, so important an 

 influence upon its erection as to merit notice 

 here. This is the external sphincter ani, or 

 more properly ' sphincter cloacae : ' it is an inch 

 and a half in breadth in the Kangaroo and half 

 an inch in thickness ; from the back of the 

 termination of the rectum it passes over the 

 anal glands and sides of the base of the penis, 

 inclosing the two bulbs with Cowper's glands 

 and their muscles, and terminates anteriorly in 

 a strong fascia above the dorsum penis, so as 

 to compress against that part the venae dor- 

 sales. 



This adjustment and function of the great 

 sphincter did not escape the observation of 

 Cowper. Speaking of the erectores penis of 

 the Opossum, he says, " the muscles of the 

 cavernous bodies of the penis of this creature, 

 having no connexion with the os pubis, cannot 

 apply the dorsum penis to the last-named bone 

 and compress the vein of the penis, whereby 

 to retard the refluent blood and cause an erec- 

 tion, as we have observed in other creatures ; 

 but some large veins of the penis here take a 

 different course, and pass through the middle 

 parts of the bulb (crus), and are only liable to 

 the compression made by the intumescence of 

 the muscles (c c) that inclose them. But the 

 chief agent in continuing the erection of the 

 penis in this animal is the sphincter muscle of 

 its anus, or rather cloaca; and not only the 

 sphincter muscle of the cloaca of the male 

 Opossum, but that of the female also, closely 

 embraces the penis in coition, and effectually 

 retards the refluent blood from its corpora caver- 

 nosa, by compressing the veins of the penis."* 

 The penis is bent upon itself in a sigmoid 

 form when retracted ; with the glans concealed 

 just within the cloacal aperture, from which it 

 emerges, as in the Ovipara, when the penis is 

 turgid and erect. 



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 (Jig. 137). The 



* Phil. Trans, vol. xxiv. 1704, p. 1584. 



ovaria are represented of their natural size in 

 fig. 138, 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 rugse and papillae. 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 (he 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 



Fig. 137. 



Ovarium and pavilion, Wombat. Natural sine. 



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 botryoidal 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- 



