Herrick, Mo7-pliolog'y of Brain of Bony Fishes. 331 



latter entirely surrounds the frontal projection of the hemi- 

 spheres. The pallium thus embraces both the olfactory and 

 cerebrum before the olfactory enters (he hemisphere (see 

 Plate XX, Figs. 1-4). 



In Siluroid fiishes the olfactory lobes are stalked in the 

 adult. The two radices are scarcely distinct before entrance 

 into the cerebrum, but at once separate thereafter. Accord- 

 ing to C Judson Herrick, the ventricles enwrap the crura 

 nearly completely throughout their course (see above for 

 details.) 



In the eel the olfactory lobes are relatively large and 

 sessile (Plate XIX, Figs. 9-11), and are overlapped by the 

 hemispheres, which are lunulate in section. The mesaxial 

 lobe is distinct but large, and receives the radix mesalis on 

 the ventro-mesal angle. The two radices appear before the 

 crus enters the hemisphere. 



In the eel, more easily than in any other fish examined, 

 the course of the radix mesalis can be clearly traced. The 

 tract preserves its identity fully, and crosses as an entirely 

 distinct bundle of the hippocampal element of the anterior 

 commissure. After decussating it reappears in the corre- 

 sponding position on the opposite side, and can be traced to 

 the medi-dorsal part of the thalamus. The radix lateralis 

 follows cephalad to the region of the anterior commissure, 

 where it turns suddenly mesad and crosses through the 

 peduncular bundles and unites with the tract of the radix 

 mesalis and decussates with the latter. The fibres of both of 

 these radices are light-colored, while the bulk of the anterior 

 commissure fibres are very dark. Horizontal sections 

 especially leave no doubt as to the course pursued by these 

 fibres, though, of course, the possibility is not excluded that 

 other connections exist, especially with the cell masses corre- 

 sponding to the hippocampus. 



In the buffalo fish (Carpiodes) longitudinal sections seem 

 to show that part, at least, of the fibres of the radix lateralis 

 pass to the hippocampel lobe. 



