240 



E. A. BAUMGARTNER 



pidonotus natrix embryo shows a well-developed Rathke's 

 pouch continuous with an anterior, thickened, slightly evag- 

 inated epithelium, the anlage of the anterior bud (fig. 35). In 

 an embryo 9 mm. long (fig. 36) there is a definite constriction of 

 the hypophysis from the oral roof. The walls of Rathke's pouch 

 are thickened and the lumen is continuous with that of the 

 well-marked evagination of the anterior lobe. The lateral buds 



Figs. 35 to 38 Median sagittal sections of the hypophyseal region of snake 

 embryos. X 40 (M. U. E. C. 570, — , — , 571 Tropidonotus natrix). 35, 6.85 mm. ; 

 36, 9 mm.; 37, 12 mm. (diameter of coil); 38, 10 cm. (total length). A, anterior 

 bud or lobe; I, pars intermedia; R, Rathke's pouch; B, brain wall; C, cartilage; 

 i, infundibulum, M, epithelium of mouth and stalk; v, veins. 



are small and not sharply separated from the caudal end of the 

 anterior evagination. 



In some Tropidonotus and Eutaenia embyros, 9.5 to 10.5 mm. 

 long, the lateral buds, which disappear in later embryos, are 

 still present. In an embryo (Eutaenia) 10 mm. in length there 

 are two very small evaginations, probably rudiments of the lat- 

 eral buds. 



A reconstruction of a 12 mm. embryo (Tropidonotus natrix) 

 shows a well developed Rathke's pouch joining, at an acute angle, 



