254 Journal of Comparative Neurology. 



little importance in consideration of the frequent and striking 

 variation which occurs in the arrangement of the terminal rami 

 of many of the nerves in Amblystoma. Furthermore, one 

 should notice that Seydel has not observed the division of the 

 proximal portion of the olfactory nerve into two distinct ele- 

 ments. This condition of the proximal end of the nerve is of 

 prime importance, since the neurones from Jacobson's organ 

 certainly enter the glomeruli by the postero-ventral element as 

 they do in Gymnophiona and Triton. 



BuRCKHARDT Considers the ventral (more caudal) root of 

 the olfactory nerve in Triton as the homologue of the ventral 

 root of the nerve in Gymnophiona. It seem to me certain that 

 this homology can be extended to the postero-ventral element 

 of the olfactory nerve in Amblystoma, and possibly to all 

 Amphibia which possess the accessory olfactory organ. The 

 anatomical distinctness of the two roots of the nerve may be 

 lost to a greater or less degree, but their morphological signifi- 

 cance, on this account, is in no wise less important. 



II. The Innervation of the Eye Muscles. 



The work of the earlier anatomists upon the Amphibia 

 has left the innervation of the eye-muscles very obscure in some 

 important respects. Even Allis {'gy) accepts the eye-muscle 

 nerves of Salamandra according to Schwalbe's ('79, p. 197) 

 observations as typical for the Urodela. Yet I have observed 

 no specimen of Amblystoma which accords with Schwalbe's 

 descriptions. The m. retractor bulbi of Amblystoma is not 

 innervated by the oculomotorius as Schwalbe reports for Sala- 

 mandra ; nor is the m. rectus internus innervated by the superior 

 ramus of the third nerve. Either there is great difference in 

 this regard between Amblystoma and Salamandra, or Schwalbe 

 has observed an extreme case of variation. However this may 

 be, the eye-muscle nerves of Salamandra according to his de- 

 scription can not be accepted as typical of Urodela. 



Herrick's ('99, pp. 391, 392) description of the oculo- 

 motor nerve of Amblystoma is correct for some individuals, 

 but it will not apply universally. The wide* variation in the 



