74 FEMALE UROGENITAL ORGANS OF PERAMELES, 



Macropodidse. So far as our present knowledge extends, Pera- 

 meles is the only Polyprotodont genus in which a direct median 

 passage has yet been found. The condition of the genital organs 

 in a pouch young of Perayale lagotis, however, suggests that such 

 also occurs in this genus. Among Diprotodonts, the direct com- 

 munication has been observed, according to Fletcher, in twelve 

 species of the family Macropodidse. That it also exists outside 

 the limits of this family, I can affirm for Tarsipes rostratus, and 

 Alix (2) states that " sur un Phascolome wombat le vagin median 

 communiquait avee le vestibule urogenital par un petit pertuis 

 bien distinct." Although I find that this is not the case in 

 Phascolomys mitchelli, yet I would not on that account venture to 

 assert that the young are not born by a median passage. As 

 regards other forms, there are some, e.g., T?'ichosurus vulpecula, 

 in which the young are almost certainly born through the lateral 

 vaginal canals, here comparatively short and simple in their 

 course, while with regard to the majority of forms, extended 

 observations based on serial sections through the termination of 

 the median vaginal apparatus are necessary before any definite 

 statements can be made concernins: them. 



'O 



Such being the state of our knowledge, it would be hazardous 

 to venture far into the uncertain field of speculation concerning 

 the conditions which first led to the acquisition of the direct 

 median passage for the birth of the young. That this median 

 passage has not been twice independently acquired within the 

 Marsupial class I am convinced, and its existence in Perameles in 

 a condition so obviously unspecialised and m association with 

 such a persistently embryonic condition of the genital organs, 

 tends to suggest that its acquisition is of ancient date, and at the 

 same time leads us to ask whether the acquirement of the median 

 passage in the first instance may not be the direct outcome of 

 some such peculiar disposition of the Miillerian ducts in the 

 genital cord as occurs in the adult Perameles and in the pouch young 

 of other Marsupials, a disposition Avithout doubt to be associated 

 with the mesial position of the ureters 1 



