214 E. A. BAUMGARTNER 



be divided into four chronological periods corresponding to the 

 prevailing theory of germ layer origin. 



In 1903, Rossi, working on Seps and Lacerta muralis arrived 

 at a number of conclusions and agreed with Gemelli ('03) that 

 the hypophysis is of ectodermal origin. 



In his 'Normal Plate' of Lacerta agilis, Peter ('04) described 

 the hypophyseal anlage in 2.8 mm. embryos of 19 segments. 

 The lateral buds are found in 3.1 mm. embryos. The hypophysis 

 is distinctly a tri-lobed body with a single stalk at 4.2 mm.; 

 the stalk has disappeared at 8 mm. Tubules appear soon after. 

 No lumen is present at 10 mm. 



Gisi ('07) gave an excellent description of the development 

 and adult anatomy of the hypophysis in Sphenodon (Hatteria) 

 punctatum. In a 15 mm. embryo there is a stalked structure 

 with several buds, of which the anterior and caudal buds are 

 prominent. A finger-like process is located below the caudal one. 

 In a 19.8 mm. embryo the stalk has degenerated and the lateral 

 buds have become compressed sagittally. In a 28.4 mm. embryo 

 the hypophysis has grown into a tubular gland and the adult 

 condition is present when the head is 12 mm. long. 



Reese ('08), describing the development of the American alli- 

 gator, mentioned a pituitary anlage in his 'stage 13' which, judg- 

 ing from his figure, is an embryo of about 6 mm. The develop- 

 ment of the hypophysis received his consideration in 1910, al- 

 though no anlage is described earlier than in a 7 mm. embryo. 

 A sagittal section of a 13 mm. embryo shows a folded sac-like 

 structure with a large outgrowth ventral to the infundibulum, 

 a small one anterior to the first, and a third extending from the 

 proximal end of the stalk. In later embryos Reese figured 

 another outgrowth lying anterior to the hypophyseal sac but 

 not connected with it. In 13 cm. alligators solid cords, com- 

 posed of densely-staining cells resembling lymphocytes, are pres- 

 ent. No lateral buds were found. 



Recently Brum" (14) published a paper on the hypophysis in 

 amniota. He studied and reconstructed the hypophysis of Gon- 

 gylus ocellata in various stages of development. A single hypo- 

 physeal anlage is described in 3.5 mm. embryos. Caudal to this 



