708 DEVELOPMENT OF THE COMMON PHALANGER, 



to leave the pouch, though for probably another month at least 

 the little one returns to the pouch for milk ; and even after the 

 young is too large for the pouch it keeps by its mother till nea)'ly 

 full grown. B}^ the following March or April the previous year's 

 young are full grown and ready to start families of their own. 



In connection with the breeding habits Mr. Scott sends me the 

 following very interesting note, which confirms my own ojiinion, 

 and to some extent explains the difficulty in obtaining intra-uter- 

 ine embryos: — " Just before giving bii'th to their young," he says, 

 " the female opossums are not out very much. My reason foi' 

 making this assertion is this — during the moon in the beginning 

 of April [full moon was on 6th April] when most of the femalf-s 

 were on the point of having their young, I found very few does 

 — nearly | of those got being bucks— whilst during the moon just 

 past [full moon 6 th May] most of those shot were does, but, 

 unfortunately, they had, with very few exceptions, already their 

 young ones in the pouch." 



As I have only a very few very early stages, and as Selenka has 

 already described very similar ova of the Rat-Kangaroo, I shall 

 in the present communication confine myself to descriptions of the 

 later intra-uterine embryos, with some notes on the mammary 

 foetuses. As the membranes in most of the stages described ha\e 

 been torn and displaced, and are in only one case moderately 

 intact, I shall not refer to these structures at present, beyond 

 remarking that in the case referred to, that of embyro D, I can 

 find no trace of a placenta, nor does the allantois appear to reach 

 the uterine mucous membrane. 



Description of Embryos. 



Embryo A (8-5 mm.). Plate xxii., fig. 1. 



I have thought this embryo worthy of description, notwithstand- 

 ing the unfortunate circumstance that the front of the head is 

 awanting, as on the whole the internal organs are very well 'pve- 

 served, and many of them are in a very interesting stage of 

 development. 



