432 JAS. P. HIJjL. 



each other by delicate partitions derived from the latter. The 

 stalks now present quite a reticular appearance ; the larger one 

 stains less deeply than the other two, and has undergone 

 marked fibrous degeneration. The nuclei are few in number, 

 and stain deeply and homogeneously. The lumina of the 

 allantoic vessels are occupied more or less completely by loose 

 branching cells. 



In two other sets of genital organs, one from a P. obesula 

 with pouch-young measuring 4 cm., I have found similar per- 

 sistent remains of allantoic stalka in the upper portion of the 

 pseudo-vaginal passage in various stages of degeneration and 

 absorption. It is not necessary here to describe the appear- 

 ances in detail. Suffice it to say that the enucleated stalks, 

 closely invested by a connective-tissue sheath, undergo marked 

 fibroid degeneration, and eventually become invaded and 

 broken up by the ingrowth of the surrounding connective 

 tissue. 



I may point out here that the existence of these remains 

 of the allantoic stalks, blocking up the pseudo-vaginal passage, 

 shows conclusively that the vesicular portion of the allantois 

 must be absorbed in utero, a view already maintained on 

 account of the presence of maternal leucocytes in it. 



Concluding Remarks. 



Before concluding this paper we may briefly inquire what 

 conclusions may legitimately be drawn from the fact of the 

 occurrence of an allantoic placenta among the Metatheria. 



Has the allantoic placenta of Perameles been independently 

 evolved within the limits of the Marsupial order or is it 

 directly and genetically related to that of Eutheria through 

 the common ancestry of the Meta- and Eu-theria from an 

 earlier diphyodont protoplacental stock ? In a previous paper 

 (18) in this Journal, on the tooth development of Perameles, 

 by Professor J. T. Wilson and myself, we incidentally touched 

 upon this question, and expressed our preference for the latter 

 of these two views; and I may here at once say that a much 

 fuller knowledge of the details of the placentation process in 



