BY JAS. P. HILL. 



T7 



(3.) The fact that the lateral vaginal canals (except their for- 

 ward expansions — the vaginal cseca), are imbedded throughout 

 their entire extent, together with the urethra, in an elongated mass 

 of connective tissue — the urogenital strand. 



(4.) The extremely short sinus urogenitalis, and the existence 

 of a very distinct cloaca. 



As regards (1) and (4) these features constitute, I think, obvious 

 marks of lowly organisation, while as regards (3), I have already 

 pointed out in the preceding pages that the median vaginal 

 apparatus in Perameles remains at a stage which is early passed 

 through in the fcetal Macropod, and which is without doubt 

 extremely primitive. As concerns (3), the adult structural 

 relations of the urogenital strand led me to believe that it 

 represented the genital cord of the foetus, and serial sections of a 

 small pouch-young at once convinced me of the Tightness of this 

 belief. The urogenital strand of the adult is simply nothing- 

 else than the persistent genital cord, from the tissue of which the 

 posterior ends of the uterine segments of the Miillerian ducts and 

 the entire vaginal 

 segments of the 

 same never become 

 free, except in so 

 far as the for- 

 wardly projecting 

 ^•aginal caeca may 

 be said to have be- 

 come free from the 

 original tissue of 

 the cord. 



Text -figures 2 

 and 3 are outline 

 drawings of sec- 

 tions through the 

 genital cord of a 



Fig. 2. 



Fig. 2 



pouch-specimen of F. nasiUa, 34 mm. in greatest length 

 represents a section through the anterior region of the cord, a little 



