BY T. THOMSON FLYNN. STS" 



Tlie embryo seemingly corresponds, in age, witii the late 

 mammary foetus of Trichosurus vulpectda, figured by Broom(2, 

 Fig. 14), of which he says it "differs but little in its character 

 from the adult." 



Genital Organs. — These are shown in Fig.2. In external 

 appearance their arrangement is similar to that of similar organs 

 in the adult(Fig.l). The ovaries are small, compressed, oval 

 bodies, quite smooth, with a length of 2 mm., and a breadth of 

 1-5 mm. Stretching back from the ovaries are visible the twa 

 genital cords, containing the Miillerian ducts and vestiges of the 

 Wolffian ducts, here confined to a short, blind passage from tlie 

 genital cord, through the mesoarium, and ending blindly in the 

 substance of the ovary. The genital cords pass back to meet 

 dorsally to the bladder. Between the Mullerian ducts pass the 

 ureters, to enter the bladder; and shortly after this, there is 

 formed, for a sliort distance, what Hill(3) has called, in the adult 

 Perameles, the urogenital strand, containing as it does the vaginal 

 portions of the INIiillerian ducts and the urethra. A little behind 

 this, however, the two Mullerian ducts open into the urogenital 

 sinus, which is directly continuous with the urethra. Most of 

 the cylindrical mass of tissue, then, seen in Fig.2, posterior to 

 the bladder, is not urogenital strand, but the enclosing tissue of 

 an extremely long and narrow urogenital sinus. It measures 

 6 mm. long, by an external width of from 1-2 mm. 



Microscopic Structure. — The Ovaries: sections show that 

 the differentiation into primitive ova and follicular cells is just 

 in progress. The M ii 1 1 e r i a n ducts are contained in the 

 genital cords. Each duct is a fairly convoluted tube opening,, 

 in front, into the abdomen by the ostium abdominale tubse, and 

 behind into the urogenital sinus. The anterior portion of the 

 duct has an average breadth, in section, of 072 mm. The 

 uterine portion of the duct is much enlarged to form the anlage 

 of the uterus. This enlargement is not visible externally. When 

 the two genital cords come together dorsally to the bladder, 

 where the two cords almost completely fuse, the two Mullerian 

 ducts remain quite distinct, separated by a wall of connective 



