Humphrey, Brain of the Snapping Tuitle. 103 



micus ventrad near the meson into the infundibulum. These 

 cells are of the true nervous type. The remaining regions 

 show the usual structure of the brain substance. The pedun- 

 cular tracts are shown lying laterad near the optic tracts 

 (Fig. 21). 



The optic tracts lie on either side of the diencephal with 

 the main portion of the fibers extending into the tectum of the 

 pregemina. A few of its fibers penetrate the walls of the dieir 

 cephal and seem to end in the geniculata and the substance of 

 the brain immediately laterad and dorsad of those structures in 

 the region probably corresponding to the pulvinar of man. 



The Infundibulum. — The general form of the infundibulum 

 is shown in Fig. 3. The base of this structure is thick and 

 contains layers of true nerve cells lying near the ental walls, 

 but its apex becomes thin walled and at the extremity is ex- 

 panded into a lobulated sac, the homolog of the sacculus of 

 other forms. The ventral wall of the distal portion is thin, 

 consisting of endyma and a very thin layer of neuroglia 

 through which the processes of the endymal cells extend. This 

 thin portion lies upon the hypophysis while the lobulated por- 

 tion overlaps the latter structure on its lateral and caudal por 

 tions. The relation of these structures in the embryo is shown 

 in figure 32. In this stage of development the distal portion 

 of the infundibulum is relatively smaller than in the adult. The 

 dorsal wall of the infundibulum is thicker and has a more truly 

 nervous structure, except at the very distal portion. Fibers 

 crossing the meson ventro-caudad of the chiasma and forming 

 the inferior commissure connect the two sides of the base of 

 the infundibulum. 



The Hypophysis. — Fig. 32 shows the relation of this struc- 

 ture to the infundibulum and the floor of the brain cavity. I 

 can find only slight evidence of any division into parts as sug- 

 gested by Gaupp (31). As this was in the advanced embryo 

 it may be possible that younger embryos would reveal the tri- 

 partite structure which he describes in other reptiles. In inter- 

 nal structure the hypophysis is composed of glandular epithe- 

 lium so closely folded upon itself that it is in the advanced em- 



