30 Journal of Comparative Neurology. 



will be found equally or more abundant, and in forms with a 

 weak development of the fasciculus communis system, they will 

 be few or wanting in the skin. In Amia the preauditory com- 

 munis component forms the palatine nerve and contributes 

 fibers to the rami maxillares infenor and superior which go to re- 

 gions where end-buds occur (Allis '95)- 



In Amiurus (Wright '84) from the fasciculus communis 

 (Lob. trig.) component are derived the most of the fibers of the 

 (l) ramus lateralis trigemini, (2) the j-amus op J ithalmicus profundus, 

 from which the nasal barblets receive their innervation, (3) the 

 ramus maxillaris, which innervates the large maxillary barblet 

 and (4) the ramus mandibidaris, innervating the mental barblets, 

 and (5) the palatine and cutaneous palatine nerves. These 

 facts, while they indicate the innervation of end-buds from the 

 fasciculus communis component, raise many difficult questions 

 bearing on the basis of homology of cranial nerves in higher 

 and lower forms. While the lobus trigemini root was consid- 

 ered as part of the Vth, the distribution of its fibers to form 

 such recognized trigeminal nerves as the ophthalmicus profundus 

 and mandibularis and maxillaris would present no great difficult- 

 ies ; but they do appear as soon as it is recognized that the so- 

 called geniculate root of the Vth of teleosts is the homologue 

 of Vllaa (Strong) of Amphibia. In Amia the difficulty is as 

 great as in Amiurus. 



It is however only when the nerve is regarded as a unit with 

 constant central connections (roots) and constant branches (rami) 

 that the difficulty has full force. Certainly suggestive in this 

 connection is Miss Piatt's work on the development of the peri- 

 pheral nervous system in Necturus. The idea that may be 

 gained there, ^ broadly stated, is that the central and peripheral 



• " I will go no further than to add that, as far as the lateral line organs are 

 concerned, their fibers choose the nearest and most direct path to the auditory 

 centers in the brain, which seem to be also the centers of the entire lateral line 

 system, yet both development and comparative anatomy tend to show that it is a 

 matter of little moment whether these fibers enter the brain by one nerve root 

 or another " Piatt, p. 505. 



" This study, therefore, leads to the conclusion that it is of little moment 

 whether the motor and sensory fibers belonging to the primitive nerves of any 



