BY R. BROOM. 711 



till it opens into the large intestine. Tliere is a distinct and 

 fairly large tliimble-shaped ctecuiu which is continuous with a 

 moderately wide dilatation of the large intestine about three times 

 as long as the csecum. From the upper end of this dilatation, how- 

 ever, the canal again narrows, and continues as a narrow tube to the 

 cloaca. The liver is well developed, and already there is a 

 distinct and well-formed gallbladder The pancreas is fairly well 

 developed. 



Urinogenital system. — The mesonephros is of fairly large siz^-, 

 but the tubules and glomeiuli are considerably smaller than in the 

 AVolffian body of an embryo sheep in a somewhat similar stage of 

 develoiiment. The peritoneal funnels of the Muellerian ducts 

 ar.^ developed, but the ducts themselves have scarcely commenced. 

 'V\u-. germinal epithelium forms a comparatively narrow layer. 

 The kidney and ureter are already indicated and differentiated 

 from each other, the kidney being present as a somewhat 

 irre,<Tular dilatation surrounded by a condensation of mesoblastic 

 cells. The cloaca is not yet open to the exterior. 



On comparing the condition of the organs in this embryo with 

 that in the embryos of Perameles, described by HilV^ it will Ije 

 seen that there is, on the whole, a very close agreement in the 

 stao-e of development, between the 8-5 mm Trichosurus embryo 

 and the 8'75 mm. embryo of Peramdes obesula. 



Embryo B (9-5 mm). Plate xxii., fig. 2. 



This embryo, which has not as yet been cut, as it is practically 

 in the same stage of development as the following one, is distinctly 

 in advance of Embryo A. The head and fore-quarters are together 

 considerably larger than the rest of the body. The head is much bent 

 on the body. The mouth is widely open and the tongue protruding. 

 The cleft of the mouth extends back to the level of the eye. The 

 nose is well formed and bears a marked resemblance to the nose 

 of the well-developed mammary foetuses, and even to that of the 



*J. P. Hill. " The Placentation of PerrtHie^e-'f," Quart. Journ. Microsc. 

 Sc. Vol. xl., p. 385. 



