the Uterine Foetus of the Kangaroo, 



483 



a, Pedicle of vitelline sac. b, Omphalo-mesenteric artery. c, Omphalomesenteric vein. 



d, Pedicle of allantois, or urachus. e, Intromittent organ, grooved below. 



umbilical vessels during their passage to the chorion: but 

 we know of no other than the allantois, or urinary bladder, 

 and urachus, as its remains are termed. The existence of a 

 placenta, in my mind, necessarily therefore infers the preexist- 

 ence of an allantois ; but the reverse of the proposition does 

 not therefore hold good. We see in birds, and scaled reptiles, 

 that the allantois itself performs the functions of the placenta, 

 or vascular chorion ; and the question to be resolved, relatively 

 to the kangaroo, and other Marsupiata was, whether the al- 

 lantois being developed, it would serve as a medium for the 

 organisation of the chorion, or remains, as in the oviparous 

 Vertebrata, an independent vascular bag, or ccecum. 



The examination of a uterine foetus of a kangaroo, kindly 



N N 2 



