CoGHiLL, Cranial Nerves of Ambly stoma. 255 



eye-muscle nerves, with regard to their exact position relative 

 to the eye-muscles, shows that no type can be established in 

 this particular without a specific study of the variations within 

 the species. And, until such a study has been made, very little 

 morphological significance should be attached to the particular 

 relation which any branch of these nerves may hold to the 

 neighboring parts. 



The intimate relation between the trochlearis and a cuta- 

 neous branch of the ophthalmicus profundus seems to be pres- 

 ent in Amphibia generally. It has led various authors to be- 

 lieve that the ophthalmicus profundus participated in the inner- 

 vation of the m. obliquus superior. Such a conclusion, how- 

 ever, seems contrary to the condition as it appears in 

 Amblystoma. 



Herrick ('94) considers that the m. retractor bulbi is 

 probably innervated by the fifth nerve indirectly through the 

 sixth, I have found no data in favor of this conclusion, unless 

 the observation of fibers passing from the ophthalmicus pro- 

 fundus into the abducens is so interpreted. None of these 

 fibers, however, were traced to the m. retractor bulbi. More- 

 over, Bowers' (1900) results speak strongly against Herrick's 

 conclusion. This author finds a |Very much greater degree of 

 separation of the sixth from the fifth nerve in Spelerpes than 

 there is in Amblystoma, and concludes that the m. retractor 

 bulbi is innervated by the sixth. Since the cranial nerves of 

 Amblystoma and Spelerpes are very similar in other respects, 

 the sixth nerves in the two forms probably have the same dis- 

 tribution. And, since the source of obscurity, the contact 

 with the Gasserian ganglion, is eliminated in Spelerpes, Bowers' 

 conclusions have special significance, 



III. The Trigeminal and Facial Nerves. 



In the terminology of the fifth and seventh nerves the 

 earlier students of the cranial nerves of Urodela have been 

 largely followed in this paper, in order to avoid the confusion 

 of implied homologies. "Alveolaris," "mentalis" and "jugu- 

 laris" are preferable, respectively, to "mandibularis internus, " 



