Misrrlhui>-n,(S. 203 



nearly a ccntimotro in lenn:th — and of u membranous expuiisioii, 

 likewiso projcctinf!; from the ])c>(liiiKle, which in its periphcrj- was 

 inseparably aniuljjaniatoil with thr eliorion. 



I was at first iiicliiu-d to rej,':ir(l the fonner vesicle as the yelk-sac. 

 From its mode of union 1 now think that it must undoubtedly be 

 re{2:arded as the nllantois. A line viuscuiar system was distinctly 

 visible upon it in the fresh state, even to the naked eye. Its contents, 

 which were in other respects limjud, contained a few turbid tiakcs. 

 Its form was spherical, and, except by its tine long peduncle, the vesicle 

 liad no attachments. 



The peduncle entered upon the right sido into the rounded mouth 

 of the peduncle of the amnios or umliilical cord, and remained for a 

 time (piite free. It was oidy far down that it united with the wall 

 so as to form a fold upon the latter, lying upon the side of the 

 amniotic peduncle turned towards the posterior ventral region (bladder 

 and penis). 



The other membranous expansion (Owen's vascuhsa) appeared to 

 be inseparably united to the left side of the amniotic peduncle from 

 its entrance iuto the latter. It contained three large vessels, pro- 

 bably two arteries and a vein, which in the peduncle lay on the 

 anterior wall and could be easily separated from the wall. One of 

 these vessels, probably the vein, united itself to the extreme loops 

 of the intestine ; the others, the arteries, passed into the interior. 



From this we must conclndo that these are vitelline vessels, which 

 alone maintain the connexion with tlie decidua, and to the support 

 of which the vitelline membrane, the outer lamina of the amnios, 

 and the chorion contribute. The state here described must, by com- 

 parison with Owen's observations, be regarded as that of the mature 

 embryo. The allantois was therefore at this time very finely de- 

 veloped, constricted into a peduncle, siirrounded by delicate vessels, 

 and with no trace of any contact with the periphery of the c)\Tim. 

 In the vascular knots of the vitelline vessels there were scattered 

 whitish deposits. At this time, when the umbilical vessels should 

 take the place of the omphalic vessels, but for want of further de- 

 velopment and attainment of attachments do not do so, the early birth 

 takes place. 



Nothing was to be observed in the way of a preparation of the 

 median sac for the further retention and nourishment of the ovum, 

 nor any thing of a preparatory dilatation of the lateral passages. 



In the ventral pouch the left teat was much longer than the right 

 one; but whether from previous sucking, or as a preparation, I 

 cannot say. 



In comparison with other embryos, that of the giant kangaroo is 

 very considerably inferior to an unborn rabbit or a newly born 

 ferret ; its size agrees pretty closely with that of an unborn mouse. 



In this comparison the small development of the hinder ex- 

 tremities is remarkable. \\Tiilst on the fore feet the five toes are 

 very distinctly formed even to the claw-tips, the hind feet resemble 

 a short-stalked fin, shghtly notched into three lobes ; the inner 

 lobe is again scarcely perceptibly divided, to correspond with the 



Ann. J!; Mcif/. X. ' '^. Vol. viii. 22 



