682 



ANATOMY OF VERTEERATES. 



537 



above-named species follow, while the size of the external pouch 

 increases in the same ratio. 



In Didelphys dorsigera the uteri, fig. 537, c, c, rather exceed 

 the unfolded vaginae in length. Each vaginal tube, e, e' , after 

 embracing the os tincae, d, is immediately continued upward and 

 outward, then bends downward and inward, and, after a second 



bend upward, descends by 

 the side of the opposite tube 

 to terminate parallel with 

 the urethra, h, in the com- 

 mon or urogenital passage, 

 f. 1 In Petaurus the vagi- 

 nae, when unfolded, are a 

 little longer than the uteri : 

 they descend close together 

 half-way toward the uroge- 

 nital passage, and there 

 terminate blindly without 

 intercommunication. From 

 the upper part of these culs- 

 de-sac the vaginae are con- 

 tinued upward and outward, 

 forming a curve, like the 

 handles of a vase, then 

 descend, converge, and ter- 

 minate close together, as in 

 the preceding example. 2 In 

 Dasyurus viverrinus and 

 Didelphys Virginiana the mesial culs-de-sac of the vagina) 

 descend to the urogenital passage, and are connected to it, but 

 do not communicate with it or with one another : each canal is, 

 then, continued outward from the upper end of the cul-de-sac, 

 and, forming the usual curve, terminates parallel to the orifice 

 of the urethra. The vaginae in the Dasyures are smaller in pro- 

 portion to the uteri than in the Virginian Opossum, but of a 

 similar form. 3 



In the Wombat (Phascolomys) each uterus communicates with 

 a separate and large vaginal cul-de-sac, the lining membrane of 

 which is increased by irregular rugae and papillae : the terminal 

 portion of each lateral canal has a thick muscular coat. The 

 urogenital canal is lined by a thick epithelium, and its surface is 



1 xx. vol. iv. p. 151, no. 2734 c. 2 xx. vol. iv. p. 152, no. 2734 e. 



8 xx. vol. iv. p. 154, no. 2738 a. 



Female organs, Didelphys dorsigera. lxxv'. 



