The Hypophysis Cerebri. 309 



vesicle and the coelia3 of the cerebral hemispheres. Figure 8 

 shows the walls of the processus infundibuH in connection 

 with the walls of the infundibulum. The walls of the pro- 

 cessus infundibuli resemble those of the hypophysis cerebri. 

 The lumen of the processus infundibuli is best shown in 

 figure 6. It contains the same kind of structureless matter 

 as the lumen of the hypoph3^sis cerebri. It is probable that 

 this structureless matter is of the nature of a secretion, and 

 its behavior with hasmatoxylin leads to the impression that it 

 is of the nature of mucous, or -pitidta. 



SUMMARY. 

 In this paper attention is called to the following points: — 



1. The term pituitary body is not S3'nonymous with hypo- 

 physis^ or hypophysis cerebri. 



2. The term infundibitlitm should not be used for processus 

 infundibuli. 



3. The epithelium lining what is known as Seessel's pockety 

 is but a single cell in thickness. 



4. The epithelium Hning the first appearance of the hypo- 

 physis cerebri is several cells in thickness. 



5. The projection between Seessel's pocket and the hypo- 

 physis cerebri is formed by a proliferation of mesoblastic cells 

 forming a nest, and is not necessarily the remains of the oral 

 plate, although it indicates the position of the oral plate. 



6. The cephalic extremity of the notochord is in close 

 connection with this nest, and does not approach the hypo- 

 physis cerebri. , 



7. The epiblast Hning the encephalon, and the epiblast 

 lining the stomodasum lie in close contact in the region of the 

 hypophysis cerebri. 



8. The hypophysis cerebri is developed from epithelium 

 on the cephalic side of the oral plate, hence is of epiblastic 

 origin. 



