THE HYPOPHYSIS CEREBRI 453 



which it arises as a pair of epithelial processes from the region 

 of junction between the main body and the stalk of the pars 

 buccalis. These grow up dorsally, and, becoming applied to 

 the surface of the tuber cinereum, increase so as to encircle 

 the pituitary stalk completely. Baumgartner (2) states that 

 in Reptiles the pars tuberalis of Tilney and also, in some cases, 

 a thin cortical zone surrounding the " anterior lobe," are 

 derived from lateral buds, similar to those of the cat and 

 chick. In Marsupials (Parker, 16) Rathke's pouch is early 

 subdivided by a constriction into proximal and distal lobes 

 (relative to the duct), and the pars tuberalis is derived from 

 the proximal lobe which grows dorsalwards around the rest 

 of the pars buccalis, branches and gives rise to a collection of 

 tubules encircling the pituitary stalk. There is thus much 

 evidence to show that there exists in many Eutheria, in Meta- 

 theria, in some Reptiles and some Birds, a special portion of 

 the pars buccalis which is developed from sprouts arising at 

 the junction of the main body of the pars buccalis with the 

 duct. This portion (the pars tuberalis of Tilney, 22) is 

 probably also represented in some fishes and Amphibia (vide 

 infra) but more detailed embryological evidence is required to 

 establish the homology throughout the Vertebrates. 



The pars tuberalis and the pars infundibularis together 

 constitute those portions of the pars buccalis which are in 

 actual contact with the nervous tissue and may accordingly 

 be grouped together as the pars juxta-neuralis. In contra- 

 distinction to this, the rest of the pars buccalis may be called 

 the pars distalis, and this forms the greater part of the epithelial 

 portion of the pituitary body and is commonly known as the 

 anterior or glandular lobe (Hauptlappen). It consists of 

 glandular tubules or columns of epithelial cells with a very 

 rich vascular supply, and it frequently includes cells of charac- 

 teristic staining capacity. Further details of its structure 

 may be most conveniently described in dealing with the 

 separate classes of Vertebrates. 



Clycostomata. — The hypophysis of Cyclostomata has been 

 described by Haller (6), Stendell (19), Sterzi (20), Gentes (4), 

 and Herring (8), amongst others. 



Herring states that the hypophysis of Myxinoids is very 

 similar to that of Petromyzon. Stendell regards that of 

 Myxinoids as partly primitive, partly reduced. 



