Z7^ 



osborn: 



[Vol. I. 



by the nutritive fluids secreted by the utricular glands, which 

 open separately by small pores. The author did not, however, 

 suggest in what manner this nutritive fluid is taken into the 

 foetal circulation. There is now no doubt from the substantial 

 agreement between Caldwell's and Selenka's observations and 

 my own, hereafter described, as to the character of the false 

 chorion in the marsupials, that the villi, which I observed at 

 the mid-period, do not continue to develop, but are transitory 

 structures, which wholly disappear, in Didelphys at least, before 

 the close of embryonic life. In fact, both Caldwell and Selenka, 



7na 



am 



/n(z 



^z 



60n 



Figure J. — PJiascolarctos cinereus. 

 Relations of the foetal membranes at an Figure 4. — Foetal membranes of the rab- 

 advanced period. After Caldwell. bit at an early period. After Kolliker. 



SO far as the observations of the latter have been published, 

 have failed to confirm my observations of the presence of villi 

 at the mid-period. I myself failed to detect any such structures 

 in several marsupial embryos, which Caldwell kindly allowed 

 me to examine in his collection. I am unable to explain this 

 discrepancy at present, unless by the fact that the villi are very 

 transitory structures, which appear and disappear in a period 

 intervening between those which have been obtained by Selenka 

 and Caldwell. However, I by no means wish to retract the 

 observations made in my former paper in regard to the presence 

 of the villi, and I believe they will eventually be confirmed ; but 

 the inferences which were drawn from them, I freely admit, are 

 now proved to be untenable. 



