Herrick, Brain of Certaui Reptiles. loi 



ing into the basal protuberance of the cerebellum. Cephalo- 

 ventrad of the optic lobe, which projects well beyond the plane 

 of section, are the two optic tr icts arching over the genicula- 

 tum. In the cerebrum, the motor peduncles can be traced to a 

 point near the front of the lateral ventricle where they curve 

 sharply dorsad and enter the cephalic part of the cerebral cor- 

 tex. The mid-peduncles of the cerebellum pass ventrad from the 

 caudo-lateral aspects of the corpora posteriora, where they ac- 

 cumulate, after decussating in the valvula, to the region ad- 

 jacent to the oculo-motor roots. The postbrachia of the optic 

 lobes appear on their way cephalo-ventrad, a strong contingent 

 passing to the inferior commissure. 



A nidulus of large nerve cells lies dorsad of the oculo- 

 motor region and receives the mid- peduncle fibres from the cer- 

 bellum. As the sections pass mesad the large tuber cinereum 

 enters the ventral part of the section and is seen to contain very 

 numerous flask-shaped cells not distinctly collected in separate 

 niduli. The ventral part of the third ventricle is expanded, 

 forming a lateral cleft-like diverticle around which numerous 

 small cells collect. The sections farther mesad cut the ruber in 

 its lateral portion and this organ may be followed nearly to the 

 median line. Fig. i Plate VII gives a good idea of the arrange- 

 ments just described. 



Fig. 2, Plate VII, illustrates a nearly median section. 

 Dorsad, the supra- and post-commissures are nearly continuous. 

 The latter is arched upon itself caudad and above it lies the syl- 

 vian commissure. The cells of the mesencephalic nidulus of 

 the trigeminus are conspicuous in the ventricular roof The de- 

 cussation of the middle peduncles is immediately dorsad of that 

 of the trochlearis tract. The niduli of III and IV lie beneath 

 the aqueduct and the former is perforated by the dorsal longi- 

 tudinal fascicle. A nidulus of very large cells lies in the median 

 line cephalad of the oculo-motor cluster. 



The front of the diencephalic roof is occupied by the 

 double paraphysis with the plexiform intrusions from them into 

 the third ventricle. 



Fig. I, Plate VIII, illustrates the relations still further lat- 



