■876 



ANATOMY AND DEVELOPMENT OF MARSUPIALIA, 



tissue averaging 019 mm. in thickness. Farther back(Fig.4), 

 ■the Miillerian ducts(^.«a^.c.) are now seen to diverge gradually, 

 but between, is a mass of connective tissue(£c) which soon remains 

 stranded between them, as shown in Fig. 5, where the Miillerian 

 ducts (J. vag.c.) are now seen to be still more separated. This 

 deeply staining mass of connective tissue(.'v) gradually disappears 

 in sections, lasting, all told, through 80. It is the indication, in 

 the embryo, of the future median vaginal cul-de-sacs (and pos- 

 sibly of a portion of, the pseudovaginal passage), passing, as it 

 does, backwards from the point where the Miillerian ducts begin 

 to diverge posteriorly. 



/ vac c 



ur 



Fig. 4. 



Fig. 5. 



The two Miillerian ducts now approach one another, and come 

 to lie parallel in the narrow cylinder of tissue continuous with 

 the connective tissue enclosing the urogenital sinus, and known 

 as the urogenital strand. Each measures on an average O-057mui. 

 in diameter. Twenty-eight sections after the disappearance of 

 the connective tissue(x), they open into the urogenital sinu.'*, as 

 shown in Fig. 6. 



The urogenital sinus has a very definite lumen, with a number 

 of longitudinal grooves; two of these are dorsal or dorso-lateral, 

 one is ventral, the others are ventral or ventro-lateral. The two 

 lateral vaginal canals open into the right and left dorsal grooves. 

 Owing to an accident, the wliole of the clitoris could not be 



