122 W. W. SWINGLE 



or that portion which takes origin from the wedge-shaped invagi- 

 nation of cells from the inner layer of oral ectoderm in the early 

 embryo, differentiates during the course of development into 

 three parts: the anterior lobe, the pars intermedia, and the pars 

 tuberalis, first recognized by Tilney ('13) as a distinct portion of 

 the gland. The remaining lobe of the gland, the pars nervosa, is 

 derived from the tip of the infundibulum. It is not wdthin the 

 scope of this paper to discuss at length the anatomical relations 

 of these parts of the hypophysis in adult Anura, especially in view 

 of the recent excellent paper by Atwell (' 19) . In figure 1 is shown 

 a ventral view of the hypophysis of the bullfrog illustrating the 

 positions of the various lobes. 



Fig. 1 Ventral view of the hypophysis of an adult Rana catesbeiana. t.c, 

 tuber cinereum; p.t., pars tuberalis; p.7i., pars nervosa; p. int., pars intermedia; 

 ant., anterior lobe. 



The pars tuberalis is seen to consist of two plaques which 

 underlie the lateral thickened portions of the tuber cinereum (in- 

 fundibulum of many writers, though it is doubtful if the lateral 

 thickened portions of this structure can properly be regarded as 

 such) . It is readily seen from the diagram that this portion of 

 the hypophysis is entirely separate from the remainder of the 

 gland. 



The anterior lobe is the most conspicuous of the remaining parts 

 of the gland, and paradoxically, instead of being the most ante- 

 rior as its name implies, it is the most posterior part of the hypo- 

 physis in the frog. Its outline is oval, and it is a delicate pink in 

 color, due to the presence of numerous blood vessels. 



