603 



This system of nerves arising by the dorsal VII. root and the first 

 root of the IX. + X. is to be distinguished, judging by the size and 

 origin of its fibres, from the sensory Trigeminus. This conclusion is 

 supported, I find, from the standpoint of distribution, by the investi- 

 gations of Ewart and Allis. The former assigns only the Facial and 

 Lateral to the mucous canals in Elasmobranchs (4) and likewise Allis, 

 in his thorough work on Amia (2), says: »the Facial is the first one of 

 the cranial nerves that takes any part in supplying the regular organs 

 of the lateral canals«. 



It is obvious that the connection of the dorsal VII. with the lateral 

 sense organs afi'ords an explanation of its disappearance in adult Anuro, 

 and also that a careful study of the relations of the internal tracts of 

 this system to those of the Auditory may throw some light upon the 

 primitive relations between the lateral and auditory sense organs. 



i. Glossopharyngeal and Vagus. 



The second main root (IX.) of this group is supplied largely by 

 the Fasciculus communis (see also 1 and 9) . There is also a small 

 ventral rootlet, probably motor. Applying the results obtained above 

 concerning the Fasciculus communis, we conclude that the fine- 

 fibred Ramus lingualis must be composed of fibres from this tract, 

 although the fibres cannot be continuously traced out. 



The third and fourth roote (X.a -{- X. è) come off close together 

 and likewise receive a large supply from the Fasciculus communis 

 which may be regarded as entering branches to the mucous epithelium 

 of the alimentary canal and its outgrowths (Rami gastrici et pul- 

 monales). There are ventral rootlets present here also. 



The fifth root (X. c) receives either a very small orno supply 

 from the Fasciculus communis and is mainly derived from the 

 Fasciculus solitari us (also 10 and 9) which is an ascending lateral 

 fasciculus and, reasoning by elimination, must be considered efferent. 



Shore (11) has insisted upon the division of the Vagus into a 

 coarse-fibred lateral and a fine-fibred visceral portion. This holds good 

 in the main, but the splanchnic motor fibres of the Vagus are, in many 

 cases, at least, coarse constituting an exception to this distinction. 



5. HypoglossuH. 



This nerve has in Chorophilus a fine dorsal root and a 

 ganglion. This appears to be also the case in early Tadpole stages 

 but in an older Tadpole examined, no dorsal root could be found 

 although there was a ganglion. It seems, however, when present, to 

 break up in the ganglion and reappear as the non-medullated com- 



