248 Journal of Comparati\e Neurology. 



decided, (') in opposition to the observations of Stieda() and 

 Schneider, () that in Amphioxus ventral motor roots were 

 lacking. 



This hypothesis appeared untenable, since, on the one 

 hand, ventral spinal nerves of a motor nature are found in 

 Amphioxus, and, on the other hand, the development ot 

 ventral nerves was observed in the region of the head, as, for 

 example, the origin of the abducens from the ventral aspect 

 of the medulla in the chick, as well as in Scyllium, by 

 Marshall. 



But, aside from the hypothesis, the fact remains that the 

 undoubtedly dorsal cranial nerves do not conform to Bell's 

 law, but are of a mixed nature. 



Van Wihje's(^) treatise, appearing soon after the works 

 of Balfour above mentioned, brougnt to light the new dis- 

 closures, known to you, concerning the ontogeny of the 

 cranial nerves in Selachians as proof, on one side, that at 

 least two pairs of muscle nerves in the head, the oculomotor 

 and abducens, appear after the manner of the ventral spinal 

 nerve roots, and, like these, innervate only muscles arising, 

 as alleged, from somites, to which the eye-muscles should 

 belong; while the motor elements of the cranial nerves 

 arising dorsally are confined to the innervation of the muscles 

 of the visceral arches, which proceed from the lateral plates. 

 Relying upon this observation. Van Wihje impeached the 

 validity of Bell's law, and showed the possibility that the 

 relations discovered for the head have further application in 

 the trunk, as in the enunciation of Bell's law the vegetative 

 muscles in the t unk proceeding from the lateral plates were 

 left out of consideration. 



While Van Wihje sought in this way to establish the 



1 " On tlie Spinal Nerves of Amphioxus," Quart. Jour. Mic. See, Jan., 1880, p. 90. 



2 "Studies on Amphioxus Lanceolatus," Mem. d. I'Academ. d. Sc. de St. Peters- 

 bourg, 1873, I. 46. 



3 " Contrib. to the Comp. Anat. and Devel. of Vert.," Berlin, 1878, p. 15. 



4 " (Jn the Mesoderrasegments and the Development of the Nerves of the Selachian 

 Head," Amsterdam, 1882. 



