148 T. THOMSON FLYNN 



carefully slit open along the ventral side without any injury 

 to the foetal membranes. It was noted that although there 

 was a close apposition of the yolk-sac wall to that of the 

 uterus, the folds of the former fitting into the hollows of the 

 latter in a very intimate way, yet there was absolutely no sign 

 of fusion or organic connexion. It will be remembered that 

 Hill, at first of the opinion that there was a protoplasmic 

 connexion between the yolk-sac wall and the uterine syncytium, 

 found later that this was not the case. 



In the case of P. gunni it was possible by means of careful 

 manipulation to make out the details of the yolk-sac circulation. 



This, at this stage, is in a state of considerable activity, 

 a condition no doubt to be correlated with the fact that the 

 allantoic placental connexion and circulation is now just on 

 the way towards completion and definite establishment. By 

 removing the lower portion of the bilaminar omphalopleure 

 and reflecting the remainder over the embryo a full view of 

 the vascular area was obtained, and the whole course of the 

 vessels could be made out in detail. After these had been 

 sketched and photographed the lower portion of the yolk-sac 

 was removed, whereupon it was found that the connexion 

 between allantoic vesicle and uterus was so slight that the 

 whole embryo with its allantois could be removed intact. The 

 point of attachment was visible in the case of this embryo as 

 a somewhat central raised area on the placental surface of the 

 allantoic vesicle. The elevation of this area was due to the 

 adherence of a slight amount of maternal tissue brought from 

 the uterine wall. 



This being the only pregnant uterus of P. gunni so far 

 known, I may be excused from entering with some detail into 

 the description of the relation of the embryonic and maternal 

 structures. 



General Eelations of Embryo and Uterus. 



Foetal Membranes. — These agree essentially in their 

 arrangement with what Hill has described for other species of 

 Perameles. For that reason I will concern myself in the 



