138 Journal of Comparative Neurology. 



connection of the sensory niduli of the thalamus is on the 

 one hand, with the cerebrum and, on the other, with the met- 

 encephalon. 



The following summary of tracts to and pom the tectum in 

 reptiles should have appeared with the preceeding instalment. 

 I. Cephalic optic tract, covering the cephalo-lateral aspect of 

 the tectum and passing to its superficial layers. 2. Caudal op- 

 tic tract, passing along the caudal aspect, in a groove between 

 the optic lobe and thalamus, to spread out upon the caudo-lat- 

 eral and dorsal regions. 3. The cephalic optic brachium, col- 

 lecting from the deeper layers and passing toward the cerebrum 

 through the geniculata. 4. Caudal brachium, with a similar 

 course. 5. Fibres of the Sylvian commissure, connecting the 

 superficial layers of the two sides. 6. The lemniscus fibres, 

 passing from the middle of the tectum to the lateral region of 

 the medulla of the same side. 7. The descending mesenceph- 

 alic tract, from the middle portions of the tectum directly cau- 

 dad into the medulla. 8. The mesencephalic root of the tri- 

 geminal. 9. The coordinating oculomotor tract, which rises 

 from the deepest regions of the cortex and passes in a slight 

 curve through the raphe into close connection with the oculo- 

 motor nidulus. All of these are clear and unambiguous in rep- 

 tiles as in fishes. 



DESCRIPTION OF PLATES. 



PLATE XV. 



Figs. i-j. Transections of the cerebrum of Menopoma, injected with gel- 

 atin through the heart. 



Figs. 4-6, Three horizontal sections from the same species 

 Fig. 7. Perpendicular section of the cerebellum of a frog larva. 

 Figs, S-g. Two horizontal sections of frog brain. 



PLATE XVL 



Fig. I. Transection of load brain cephalad of chiasm, prepar. preparaphy- 

 sis; supr, c. supracommissure tract on its way to rhinalis sinus in cerebrum; .r, 

 thalamic branch of commissure of habena? tract; v. ped. ventral or motor ped- 

 uncle. 



Ftg, 2. Section of same brain at precommissure. Hipp. c. hippocampal 

 commissure tract ; call, callosal fibres ; striatum, portion only of this body ; olf. 

 radix, fibres from the olfactory radix at point of division. 



