354 MR. OWEN ON THE GENERATION OF THE MARSUPIAL ANIMALS. 



The last form of the marsupial female organs which may be noticed is that which 

 is found in the Kangaroo Rat (Hypsiprymnus Wkitei), where they present the most 

 extraordinary appearance (PI. VI. fig. 6.). The type of construction is, however, the 

 same as in the great Kangaroo, but the mesial cul de sac of the vagina attains a still 

 greater development ; it not only reaches downwards to the urethro-sexual passage, 

 but also upwards and outwards, dilating into a large chamber, which extends beyond 

 the uteri in every direction. From the sides of this chamber the separated portions 

 of the vagina continue downwards, to terminate, as usual, in the urethro-sexual canal. 



In all the preceding genera the structure of the uteri is as distinct from that of 

 the vaginse as in the Rodentia. The fibrous or proper tunic of the uteri is thicker 

 than that of the vaginae, and the lining membrane is soft and vascular, and disposed 

 in numerous irregular folds, which in section give apparently a still greater thick- 

 ness to the uterine parietes. The whole extent of the vaginse, on the contrary, is 

 lined with a thin layer of cuticle, which is readily detachable, even from the middle 

 cul de sac, so generally considered as the corpus uteri in the Kangaroo. 



The inner surface of the culs de sac in the Opossum is smooth, but in the lower 

 part of the single cavity in the Kangaroo and Kangaroo Rat it presents a reticulate 

 structure. The lining membrane in the lateral canals in all the genera is disposed 

 in regular longitudinal folds, a disposition which characterizes the true vagina in 

 most of the ordinary quadrupeds. In the Kangaroo, as in the other Marsupiata, the 

 lateral canals communicate with the common or urethro-sexual cavity without 

 making a projection ; but at the distance of three fourths of an inch from their ter- 

 mination there is a sudden contraction, with a small valvular projection in each, 

 which probably limits the extent to which the bifurcated glans is introduced in 

 coitu. By those who consider the cul de sac and lateral canals as a modification of 

 the corpus uteri, these projections will probably be regarded as severally representing 

 an OS tincse ; but as they do not exist in the Opossums and Petaurists, in which there 

 is simply a contraction of the vaginal canals at the corresponding part, and as in 

 both these, as well as the Kangaroo, the true uteri open in the characteristic valvular 

 manner, as in the Rodentia, without the slightest appearance of a gradual blending 

 into the vaginal cul de sac, the above structure cannot be regarded as materially 

 affecting a determination supported both by the general texture and connexions of 

 the part in question, as well as by what is now ascertained to be its limited function. 

 Moreover, in the large single vagina of some of the Rodentia, as the Hare, Rabbit, 

 and Paca, there are two corresponding valvular folds of membrane near its com- 

 mencement, a little way above the urethral aperture, which Daubenton consequently 

 regarded as the limits of the corpus uteri. 



In endeavouring to trace the purposes answered by the different forms of the 

 female marsupial organs above described, considerable difficulty arises from the want 

 of the necessary evidence which would be afforded by the examination of the pregnant 

 uterus in each of the genera, and by the absence of information as to their respective 



