Kingsbury, Brain of Nectmus. 189 



In fine, in Auiphibia, the "dorsal VII " and "dorsal IX" 

 (IX^+'), both terminate in the dorsal region of the oblongata, 

 in the immediate neighborhood of the eighth nerve and in large 

 part slightly caudad of it. 



Abducens Neive. — This is very small in Nectur2ts and arises 

 from the ventral aspect of the oblongata by two very small 

 roots. I was unable to trace it to its nidus. In Amblystonta, 

 though the nerve is much larger and arises by three roots, no 

 direct relation to a nidus could be observed. The fibers sprang 

 apparently from the posterior longitudinal fasciculus. Undoubt- 

 edly the motor cells of the ventral region in this immediate 

 neighborhood constitute the nidus of origin. 



Ttigeviiniis. — The fifth nerve is the largest of the nerves 

 arising from the oblongata ; and, save the olfactory, of all the 

 cranial nerves. The fibers of which it is composed are drawn 

 from four sources, and leave the brain by three ill-defined roots. 



(i). Ascending V. This furnishes by far the largest por- 

 tion of the fibers of the fifth in Nectunis. It can first be dis- 

 tinctly recognized in the myel a slight distance caudad of the 

 second spinal nerve, where it occupies a dorso-lateral position. 

 In this region it is small. At the level of the first spinal nerve, 

 it has increased in size and from this point cephalad begins to 

 migrate ventrad. At the level of X^ its position is lateral and 

 the fibers of the tenth pass through it. At the eighth it is 

 ventro-lateral, the eighth arising dorsad of it. Its fibers are 

 mostly small, although a considerable number of large ones 

 occur in it, some of which can be traced from its first appear- 

 ance in the caudal portion of the myel. No augmentation by 

 fibers from motor nidi was observed, and it is presumably purely 

 sensory. 



(2). Sensory nidus (terminal). Cephalad of the exit of 

 the dorsal seventh, fibers arise among the cells adjoining the 



very small. In Plethodon no trace of it was found and the roots of the lateral 

 line nerves are believed to be absent. Pinkus did not examine the ental origin 

 of the lateral line roots in Protopterus, but the ectal relations shown by him and 

 the results of Burckhardt ('91) indicate a close resemblance to the conditions 

 in the Amphibia. 



