176 Journal of Comparative Neurology and Psychology. 



the olfactory mucous membrane, they hear a ganglion on their course 

 and centrally, in most if not in all cases, they do not connect with 

 the olfactory bulbs but with the brain farther caudad in the vicinity 

 of the recessus preopticus or lamina terminalis. It may, therefore, 

 be concluded that, while the nervus terminalis occurs in fishes gen- 

 erally, its presence has not hitherto been demonstrated in the adults 

 of any forms above the fishes. 



In examining preparations of the brain of the frog prei)ared by 

 the Golgi method I found an impregnation of nerve fibers which 

 conform so closely to the central course of the nervus terminalis 

 of selachians and dipnoans that I have no hesitation in consider- 

 ing them homologous. In the first series of sections in which this 

 nerve was seen its fibers were completely impregnated on both right 

 and left sides from a position rostrad of the olfactory bulbs to 

 their decussation in the lamina terminalis ; and, since the olfactory 

 nerves and tracts were for the most part unimpregnated, the course 

 of the nervus terminalis could be followed with precision. These 

 findings were subsequently verified in several series of adult and 

 larval frogs, as follows: 



Transverse sections of adult Kana i)ipiens by the Golgi method 

 (the series referred to above, Figs. 1 to 7). 



Sagittal sections of adult Ttana ])i])i('ns by the Golgi method. 



Transverse sections of the adult Rana pijiiens by the Weigert 

 method. In this series the ])rocess of decolorization of the sections 

 was incompletely carried out, leaving considerable color in the back- 

 ground, so that, though the intra-cerebral course of the nervus ter- 

 minalis is unmedullated, the course of the tract could neverthe- 

 less be followed with precision. Other series of Weigert sections 

 permitted the nerve to be identified where it enters the brain, but 

 not through the brain substance, on account of the complete decol- 

 orization of its fibers. 



Transverse sections of a half-grown frog tadpole by the Golgi 

 method, illustrating the w^hole central course of the neiwe and its 

 free terminal arborizations in the lamina terminalis (Figs. 9 and 

 10). 



Horizontal sections of an old larva of Rana catesbiana 30 mm. 



