248 Journal of Comparative Neurology. 



resulting nerve is distributed to the skin of the upper surface of 

 the third external gill. This anastomosis is probably charac- 

 teristic for larvae of certain stages, but in individuals with the 

 external gills much reduced in size the anastomosis does not 

 occur, and the branch to the external gill is very small. 



VII. Resume of Part I. 



The element of the olfactory nerve which innervates 

 Jacobson's organ arises from the postero-ventral portion of the 

 area of exit of the entire olfactory nerve. It is fused for a 

 considerable distance with the element which innervates the 

 olfactory epithelium proper. None of the branches of the 

 olfactory nerve receive medullated fibers from the trigeminus. 



The innervation of the muscles of the eye is from four 

 sources : from the third, fourth and sixth nerves, and from the 

 r. ophthalmicus profundus V. The superior ramus of the third 

 nerve supplies them, rectus superior; the inferior ramus, the 

 recti inferior et internus and the obliquus inferior. The 

 obliquus superior is innervated wholly by the fourth nerve. 

 The sixth nerve innervates the m. rectus externus and m. 

 retractor bulbi. The central relation of the neurones which 

 innervate the m. levator bulbi can not be stated positively, but 

 they appear to be derived from the r. ophthalmicus pro- 

 fundus V. 



The auditory nerve arises by two roots. The lateralis VII 

 root, arising dorsally of the latter, forms into an anterior and a 

 posterior division. The ganglion of the anterior division is on 

 the dorsal surface of the Gasserian ganglion and gives rise to 

 the r. ophthalmicus superficialis VII and the r. buccalis VII. 

 The ganglion of the posterior division is on the hyomandibular 

 trunk, near the lateral border of the ear capsule. It gives rise 

 to the r. mentalis VII. The communis VII root arises dorsally 

 of the ventral VIII root and anteriorly of the dorsal VIII root. 

 It bears the facial ganglion which gives rise to the r. palatinus, 

 r. palatinus caudalis, r. alveolaris, and sometimes to a small 

 nerve to the r. pre-trematicus IX. The motor VII root arises 

 ventrally of the others and enters the hyomandibular trunk. 



