124 Journal of Comparative Neurology. 



9, lat. tub., Plate XVI). In Necturus there are a few scattered 

 fibres on the very ventral surface which run directly caudad to 

 beyond the chiasm — probably to themammillary region. These 

 fibres have not been elsewhere encountered. 



The hippocampal region of Necturus has proven susceptible 

 to a stain which brings out the cellular relations with all desira- 

 ble completeness. It is possible to trace the axis cylinder fibres 

 from the scattering cells of this lobe into the tracts which col- 

 lect to unite in the fornix commissure. It will be noted that in 

 the figure the protoplasmic processes spring from the same end 

 or the opposite end of the cell depending on the position of the 

 cell. (Fig. I, Plate XX.) 



The above connection is precisely that which we have de- 

 termined in reptilia except that in the latter case the hippocamp- 

 al cells have assumed the secondary relation, i. e. , have retreated 

 from the ventricle in a body and, as a consequence, the axis 

 cylinder processes have gathered entad of the cells while in am- 

 phibia the cells have departed little from their embryonic condi- 

 tion and the fibres remain ectad of the mass of cells. If these 

 tracts are, as appears, homologous with the fimbria we have in 

 the conditions prevailing in lower vertebrates a strong presumpt- 

 ive evidence in favor of the writer's position that fimbria fibres 

 arise from the cortical cells of the hippocampus. Compare Fig. 

 13, Plate XX, which is a portion of the hippocampus of the 

 black snake. 



The white matter and tracts of the fore-brain and dienceph- 

 alon of amphibians has received an exhaustive treatment at the 

 hands of Dr. Edinger, which resulted in the statements sum- 

 marized below. ^ 



Connections with the prosencephalon, i. The basal pros- 

 encephalic bundle (so also Osborn, Koppen's " round bundle,") 

 Schulgin's "Tract P." or analogue of the pyramids. Osborn 

 speaks of a branch to the thalamus as "infundibular tract," 

 which Koppen terms " Thalamus Tuber cinereum Bahn." 



2. Taenia thalami, or tractus ganglii habenulae ad prosen- 



lUntersuchungen u. d. vergl. Anatomic des Gehirns, 2. 1892. 



