THE HYPOPHYSIS IN REPTILES 237 



attached to the floor of the anterior lobe projects ventro-cau- 

 dally and is continuous with the pharyngeal roof. The lateral 

 lobes have many tubular outgrowths at their free ends. The 

 tip of Rathke's pouch has curled about the infundibular out- 

 pouching. 



The hypophysis in a 28 mm. embryo bears little resemblance 

 to the sac-like outgrowth of the younger embryos (fig. 25). 

 There is a small cavity in the caudal portion of the anterior lobe 

 continuous with that of Rathke's pouch. The remainder of the 

 organ is made up of cords with occasional lumina indicating a 

 tubular development. A prominent caudal tubular evagina- 

 tion of the floor of the anterior lobe extends above, and another 

 below the anastomosing branch of the carotids. Between the 

 former and the tip of Rathke's pouch is the anterior end of the 

 the notochord. The hypophyseal stalk extends ventro-caudally 

 from the floor of the anterior lobe. Near its oral end it makes 

 a sharp ventral bend and joins the pharyngeal epithelium. 



A series of drawings of the hypophysis of a transversely sec- 

 tioned embryo, at least 30 mm. in length, is shown in figures 

 27 to 29. The relations and extent of the anterior lobe and lat- 

 eral buds can be seen. Lumina are present in some of the 

 glandular outgrowths of the anterior lobe, but the lateral buds 

 are solid. The pars intermedia is ventral to the infundibulum. 



In a 12 cm. embryo, Rathke's pouch curls around the dorsal 

 side of the well-developed infundibular evagination (fig. 26). 

 The pouch is constricted in its middle, and its antero-ventral 

 end is continuous with, and forms part of, the anterior lobe. 

 The latter is now one large mass of cords, continuous laterally 

 with cords developed from the lateral buds which extend dor- 

 sally and join across the median line. Many cords with free ends 

 project cranialward and caudal ward from the floor of the an- 

 terior lobe, A caudal cord lies just below the anatomosing 

 branch of the cerebral carotids which is crowded against the 

 caudal surface of the anterior lobe. From about the middle of 

 the ventral floor of the latter lobe the hypophyseal stalk extends 

 caudalward and, passing through the bony basis cranii, is con- 

 tinuous with the oral roof. It still shows a sharp bend ventral- 

 ward before the oral roof. 



