THE GREATER KANGAROO. 



animal, I trust the reader will pardon me for introducing the 

 following technical details. " In a paper read before the Royal 

 Society in January, 1834, Professor Owen described the foetus 

 and membranes of a specimen of the greater kangaroo, at 

 apparently the middle period of uterine gestation, which in 

 this animal lasts thirty-eight days. The membranes consisted 

 of an amnios ; a very large vitelline sac, rendered highly 

 vascular by ramifications of omphalo-meseiiteric vessels, and 

 a thin unvascular chorion. There was no placenta* nor any 

 adhesion between the exterior membrane of the foetus and 

 the internal surface of the mother, by the opposition and 

 interlacement of villi, or vessels, as in those mammals in which 

 the placenta is replaced by a uniform villous and vascular 

 chorion 5 the condition of the foetus was, in short, such as 

 obtains ire the viper and other ovo -viviparous reptiles ; save that at 

 the period of development at which the foetus in question had 

 arrived, there was no trace of the existence of an allantois. 

 To ascertain whether an allantois was developed at a subsequent 

 period of uterine gestation, he dissected very young mammary 

 foetuses of different marsupial animals, as the kangaroo, Phalan- 

 gista, and Petaurus ; and finding in them the remains of a 

 urachus, and umbilical vessels, he concluded that an allantois 

 was developed at a more advanced stage of the development of 

 the embryo. He observed, that as the growth of the foetus 

 advanced, the circulating fluids became necessarily more charged 

 with decomposed particles of the organized substance > 9 and that 

 although the extended surface of minutely subdivided blood- 

 vessels, afforded by the vitelline sac, might serve both for respi- 

 ration and nutrition at the earliest stages of development, yet 

 that, at a late period, an accessory apparatus to that end ap- 

 peared to be necessary, as the embryo acquired additional bulk 



* In the Universal Magazine of August, 1808, I find it stated that Mr. 



Home, on dissecting a trombac (DideJphis ), found that it had two uteri; 



and that Mr. Bell, a surgeon of New Holland, dissected one in a pregnant 

 state, and discovered in the uteri a gelatinous substance, conveyed in two 

 tubes, instead of a placenta. J. H. F. 



