882 



ANATOMY AND DEVELOPMENT OF MARSUPIALIA, 



it on the outer side; on the right side, the median vaginal neck 

 enters the cul-de-sac from its outer side, and leaves it by the outer 

 side. 



The peculiar and irregular arrangement indicated here, points 

 to one of two conclusions. 



(i.) That, in this Marsupial, the median vaginal cul-de-sacs are 

 not present in the virgin, and that they are mechanically caused 

 by the resting of the embryos in their course outwards; or, 

 which is more probable, 



(ii.) That the enlargement of the median vaginal cul-de-sacs, if 

 present in the virgin, is not a result of conception, but a mechan- 

 ical result of the passage of the embryo itself. 



Of these, the first is virtually disproved by the presence of 

 the epithelial lining to the median vaginal cul-de-sacs. 





Fig. 8. 



Fig. 9. 



We have now in section, therefore, two median vaginal cul-de- 

 sacs lying side by side, but separated by a fairly thick wall, 

 which becomes still thicker further back. Posteriorly the median 

 cul-de-sacs terminate blindly in irregular spaces similar to those 

 in which they began. Tliere is no sign of any inter-communica- 

 tion between the vaginal cul-de-sacs, the intervening partition 

 being quite complete and unperforated. A study of Fig.9, some 

 sections behind Fig.8, shows that this form exhibits, in common 

 with Peramele$, that primitive arrangement in which the posterior 



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