THE HYPOPHYSIS CEREBRI 459 



of the development of the Reptilian hypophysis, and has also 

 given a description of the adult anatomy as well as a review 

 of the literature dealing with this group. 



The pars neuralis is well developed and forms an outgrowth 

 which is hollow in most forms, but is solid in some snakes. 

 This is closely invested on its ventral and postero-ventral faces 

 by the pars infundibularis. There is no cleft separating the 

 pars infundibularis from the pars distalis, but Baumgartner 

 states that in some lizards a remnant of the original lumen of 

 Rathke's pouch persists as a cleft in the substance of the pars 

 intermedia. 



The pars distalis has, according to Herring (8), a structure 

 peculiar to Reptiles. It consists of columns of cubical or 

 columnar cells forming distinct acini, the cavities of which 

 are filled with a homogeneous colloid material. Two types 

 of cells are recognisable, the majority being clear and non- 

 granular, others being granular and readily stained. 



In early stages of the development of some members of 

 each group of reptiles, the primordia of a pars tuberalis are 

 recognisable as lateral buds arising from Rathke's pouch. 

 According to Baumgartner (2) in turtles these lateral buds 

 persist and form a pars tuberalis lying against the tuber 

 cinereum, dorsal and anterior to the pars distalis, and also a 

 cortical zone around the anterior part of the pars distalis ; in 

 alligators they form a tongue-like process (pars tuberalis) and 

 a spiral band around the pars distalis ; in Sphenodon (Gisi, 5) 

 they form a " pars terminalis " (equivalent to pars tuberalis) ; 

 in most lizards and snakes they disappear completely. Baum- 

 gartner points out that on embryological and histological 

 grounds both the cortical zone in turtles and alligators and 

 the separate cell masses derived from the lateral buds must 

 be included in the pars tuberalis. These latter cell-masses 

 are paired and appear to resemble closely the cell-strands in 

 Amphibia to which reference is made above. The pars 

 tuberalis, according to Baumgartner, consists of irregular 

 columns of cells, separated by a large amount of vascular con- 

 nective tissue. 



The pars buccalis in Reptiles develops from a typical hollow, 

 ectodermal pouch, whose walls become differentiated into pars 

 infundibularis and pars distalis, while, as already stated, lateral 

 buds arise which in some cases persist and form a pars tuberalis. 



