Kingsbury, Brain of Nectmus. 197 



Summary, 



1. As compared with certain smaller urodeles, the brain 

 of Necturus is greatly elongated. This appears to be due 

 largely to a greater inequality between the rates of growth of 

 the brain and skull. This is shown, it is thought, especially by 

 («) the almost entire absence of a pons flexure, (<5) the length 

 of the olfactory nerves, (^) the extent of the diatela. 



2. A callosum is considered to be entirely absent in the 

 amphibian brain : what has been generally regarded as such 

 is here thought to be a hippocampal commissure, in part at 

 least, although the homology should be dependent on compara- 

 tive study. 



3. An olfactory tract upon the extreme ventral surface of 

 the cerebrum may be traced to the region just caudad of the 

 the infundibulum, — presumably the region of the albicantia. 



4. The paraphysis is well developed and in communica- 

 tion in the adult with the encephalic cavities. The postpara- 

 physis of some authors is not regarded as a true evagination. 



5. The fiber relations in the oblongata have been inves- 

 tigated to a certain extent ; especial attention having been paid 

 to the posterior longitudinal fasciculus, the dorsal tracts, lem- 

 niscus and the arcuate fibers. 



6. The ental origins of the cranial nerves are worked out 

 more or less completely. For general results Tables on pages 

 179 and 191 may be consulted. In particular, the motor por- 

 tion of the facial nerve is shown to have the same mode of 

 origin as in the majority, at least, of vertebrates. The first 

 two roots of the vago-glossopharyngeal group, stated to be the 

 representative of the lateral nerve of "fishes," and the nerve 

 termed "dorsal seventh, " are composed of fibers of the same 

 appearance and terminate in the dorsal region of the oblongata 

 in the neighborhood of the eighth nerve. 



7. Mauthner fibers were demonstrated in the adult Nee. 

 Uinis, Amblyst07na and Diemyctylus. Amblystovia is a land form, 

 hence there is no direct correlation with an aquatic mode of life 



8. A ligamentmn denticulatiun is present in Necturus. 



9. The mesencephalic pit is well marked in Necturus. 



