70 FEMALE UROGENITAL ORGANS OF PERAMELES, 



In view of the fact that both in Perameles and in cei'tain 

 Macropods [cf. especially Stirling (10)], the young reach the 

 exterior by way of a direct median passage, involving in both 

 cases the median vaginal apparatus, the question next arises, may 

 not the mode of formation of the direct passage in Perameles, 

 associated as it is with such an extremely primitive condition of 

 the median vaginal apparatus, tlu'ow light on the parturition 

 phenomena in those other Marsupials with a direct mode of birth, 

 and in particular, may there not occur, in the parturition of 

 Macropods, phenomena recalling the formation of the pseudo- 

 vaginal passage in Perameles ? 



Now it has been shown by numerous independent investigators, 

 from Home (14), who first described the condition, onwards [I 

 need here only cite the careful work of Lister and Fletcher (11), 

 and Fletcher (12 and 13), whose papers contain, in addition to 

 their own extensive observations, valuable historical summaries of 

 the earlier investigations in this field], that in many species of the 

 family Macropodidoi, a direct post-partum communication exists 

 between the median vagina and the urogenital sinus, that there- 

 fore the young reach the exterior in those forms in which such an 

 opening exists by a direct median passage as in Perameles. 



Only in two cases has the median vagina in Macropods been 

 found to communicate with the urogenital sinus in virgin animals, 

 namely, " by Lister in H. ualabatus and Brass in II. hennettii " 

 (Fletcher, 13, Part ii. p. 9), but such cases are to be regarded as 

 very rare and exceptional variations. 



In virgins, normally, as Fletcher's investigations (13) show, the 

 median vagina ends blindly in the connective tissue between the 

 posterior ends of the lateral vaginal canals and in comparatively 

 close proximity to the urogenital sinus. Figures such as the 

 classical figure of Owen of the genital organs of a pregnant M. 

 major (9, Plate vi., fig. 7), and certain of those of Brass (4, 

 notably fig. 2, Taf. ii., representing the vagina? of a young 

 Trichosurus, fig. i., Taf. iv. representing the genital organs of 

 Phascolomys, and fig. i. Taf. iv. those of 31. major), are, as Fletcher 

 has already pointed out (13, Part i. p. 658), entirely misleading 



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