578 



PRELIMINARY NOTE ON THE OCCURRENCE OF A 

 PLACENTAL CONNECTION IN PERAMELES OBE- 

 SULA AND ON THE FCETAL MEMBRANES OF 

 CERTAIN MACROPODS. 



By Jas p. Hill, Demonstrator of Biology, in the University 



OF Sydney. 



(Plate XLix.) 



Some little time ago there came into my hands, through the 

 kindness of Mr. A. M. Lea, a female short-nosed Bandicoot, 

 Ferameles obesula, which proved, on examination, to be pregnant. 

 Two embryos were found in the left uterus, and one, the largest 

 of the three, in the right. This latter embryo measured 8-75 mm. 

 from end to end of the curved body. 



On opening the uteri it was found to be impossible to remove 

 the embryos without tearing the foetal membranes, and so two of 

 them were preserved enclosed in their membranes and attached 

 to portions of the uterine walls. 



Recently I have had the opportunity of examining these 

 embryos in some detail, both macroscopically and microscopically 

 in serial sections, with the result that a true allantoic placenta 

 was discovered. 



The foetal membranes need not be specially considered in this 

 note, since they have essentially the same general arrangement 

 as those of Fhascolarctus and A^^pyprymnus, recently described 

 by Prof. R. Semon.* As in these forms the embryo is sunk into 

 the yolk sac, and is partially surrounded by the invaginated 

 upper portion of the yolk sac wall consisting of splanchnopleure 

 (splanchnic mesoderm and entoderm), and distinguished by Semon 

 as the "inneres Blatt." This inner leaf does not, however, so 

 completely surround the embryo in Peraineles as in Macropus, 



* Zoologische Forschungsreisen in Australien. Zweiter Band, Erste 

 Lieferung. Monotremen unci Marsupialier, von R. Semon. 



