An Analysis of the Justa-Neural Epithelial Portion etc. 277 



a solid stalk [19] and the two caudal projections. The cavity con- 

 tained in this structure is still large; it extends from the body into 

 the neck and the two projections. More significant than these changes 

 is the appearance of the epithelial processes from the two lateral 

 borders of the dorsal surface in the region where the neck of the 

 pars buccalis joins the body. Each of these processes is a sprout 

 which is growing dorsad. Since its further development shows that 

 it is the anläge of the pars tuberalis, it may for this reason be 

 referred to as the tuberai process [30]. It is to the growth of this 

 process and to the change in relations which it occasions that especial 

 attention will be directed in the descriptions which follow. 



The only noteworthy modification in the neural portion of the 

 hypophysis to be observed in this stage is the cephalic extension of 

 the infundibular process [28] in such a manner as to indent the 

 caudal surface of the pars buccalis. The floor of the third ventricle 

 also shows a modification of some importance in that there rises from 

 its dependent portion a plateau-like elevation which passes out into 

 the optic recesses. This elevation is the post-chiasmatic process; it 

 marks the cephalic limit of the recessus tuberis- 



17 mm Cat Embryo no. 259. The conditions in this stage have 

 changed but little as compared with the embryo just described. The 

 several divisions of the pars buccalis are still well marked. The 

 body, neck, stalk and caudal projections have the same general rela- 

 tions. The body has increased relatively in size and is further altered 

 by a tendency of its dorsal surface to depart from its earlier juxta- 

 neural position. This is determined by the occurrence of two well 

 marked lateral invagin-ations of this surface along the lines already 

 indicated in the 14 mm stage as lateral furrows. As a result of 

 these invaginations the dorsal surface now presents a median elevated 

 ridge still in contact with the diencephalic flooi-, while lateral to this 

 ridge, and representing the major portion of the dorsal surface, are 

 two deep gutters, one placed on either side, with its long axis parallel 

 with that of the median ridge. The regions of these two gutters 

 have entirely lost their juxta-neural position. This change is un- 

 doubtedly due to the manner and rate of growth in the tuberai sprout. Each 



