177 



in 20 geiieia of shaiks and rajs. At first he held the nerve to be 

 a part of the olfactory nerve, bnt later on he recognised its homology 

 to the new nerve of Pinkus, and called it the N. Terniinalis. 



In the Selachii tiie distance between the nasal sac and the olfactory 

 bulb is small, hence tiie olfactory nerve is short. Immediately on its 

 appearance out of tiie nasal sac it is separated into a lateral and n 

 mesial bundle by a sniall groove into which the disial termination 

 of the N. Terminalis enters. 



Scoliodon terrae novae alone has something peculiar. Here the 

 two bundles are not only completely separated from each other, but 

 the division also continues on to the bulb, and even to the distal 

 (foremost) end of the tract, which usually is long in the Selachii. 

 After the N. Terminalis of the Selachii has made its appearance out 

 of the hemisphere, it takes its course along the mesial border of 

 the tract, and when it has reached the bulb it forms a ganglion. 

 In some species two ganglia were observed in the coui-se of the nerve. 



LocY assures that the nerve in its distal ramifications is principally 

 limited to the olfactory mucous membrane, but to my mind he has 

 not proved this. His method was not sufficient to do this, and 

 considering the results of other investigators in other classes of 

 animals this assertion needs cori'oboration by preparations treated 

 with silver compounds. 



In the Ganoids the N. Terminalis was first found and clearly 

 represented by Phelps Alt, is (1897, fig. 64) inAmiacalva. He could 

 follow it caudal ly up to the fore-brain. In the larvae he also found 

 its ganglion. 



In J 910 Brookovkr described its development in these fishes. His 

 investigation contains many new finds and interesting communications, 

 bnt his conclusion that the nerve is a branch of the olfactorj' nerve 

 cannot in my opinion be correct. In his work in J 914 on the nerve 

 in Lepidosteus he also came to this conclusion. 



In the Tekostei Sheldon and Brookover (1909) found the nerve 

 in the carp and in Amiurus. According to them the roots of the 

 ganglion enter the olfactory bulb to reach the hemisphere, contained 

 in the tract. Here however the question ai-ises whether they have 

 not made a mistake analogous to that of de Vries in the embryos 

 of man, as this is not the condition in the Dipnoi, in the Selachii, 

 in the amphibians or in the mammals, nor either in man according 

 to what Brookover himself (J 914) found in the last-named. 



Concerning the lungfishes I can here demonstrate to you two fine 

 models of the fore-end of the brains, with the nerves arising there- 

 from, of Ceratodns and Protopterus, both constructed by Dr. van der 



12 

 Proceedings Royal Acad. Amsterdam. Vol. XXI. 



