419 
which are found among the placental mammals. The difference is one 
of degree only, the embryos are minute, so are the villi, yet in each 
embryo they could be plainly seen with the naked eye. It must be 
noted that these villi were confined to that portion of the subzonal 
nembrane to which the yolk sac was attached and were not found else- 
where; also that in the case of the Opossum embryos, which were ob- 
cerved in situ, the villous area was in close contact with a furrow in 
the uterine wall, while the other portions of the subzonal membrane 
were free. This contact was not so close as to be called an »attach- 
ment«, for a slight touch with the needle freed the embryos, from their 
position. An unfortunate accident prevented a satisfactory study of the 
uterine wall which was very desirable in order to ascertain whether 
anything in the nature of Crypts were present for the reception of 
these villi. 
I think it may be safely inferred from these facts that the functions 
of the Allantoic placenta in the higher mammals are performed in a 
feeble way by the yolk sac of the Marsupials, the process agreeing 
precisely in kind but differing in degree. The subzonal attachment of 
the Allantois in one of the embryos, which was not so positively de- 
termined, may indicate the first step towards the transfer of the function 
of nourishment from the yolk sac to the Allantois. 
The bearing which these features have upon the early history and 
evolution of the placenta is obvious, but a discussion of these questions 
must be reserved for a more extended paper. 
4, Das Os intermedium tarsi der Säugethiere. 
Von Professor Dr. Paul Albrecht in Brissel. 
Im Anschlusse an die ausgezeichnete Arbeit des Herrn Professor 
Dr. Bardeleben über das Os intermedium tarsi der Säugethiere ! er- 
laube ich mir zu bemerken, daB ich selbst schon seit vielen Jahren 
diesen Knochen gefunden, die Veröffentlichung meiner Ansichten über 
denselben aber noch immer hinaus geschoben habe. 
Da es mir selbstverständlich völlig fern liegt, Herrn Professor Bar- 
deleben die verdiente Priorität streitig zu machen, so wird es mir 
doch, wie ich hoffe, gestattet sein, bei dieser Gelegenheit die von ihm 
mitgetheilten Thatsachen zu bestätigen. Da ich den Bardeleben- 
schen Ausdruck Os trigonum für den betreffenden Knochen sehr gut 
gewählt finde, so will ich auch von jetzt an denselben in dieser Weise 
bezeichnen. 
1 Zoologischer Anzeiger No. 139. 
