No. I.] THE CRANIAL NERVES OF AMPHIBIA. 175 



out by Allis in Amia, and later by the writer in the tadpole, 

 of supposing that the Trigeminus takes part in the innerva- 

 tion of the lateral sense organs of the head, an error repeated 

 in most of the text-books. 



In treating of the roots, Marshall and Spencer come to the 

 following conclusions : The fifth nerve in the adult arises by 

 two roots : («), an anterior non-ganglionic arising by two root- 

 lets (V7) = "ist root of Stannius, the anterior root (V«) of 

 Gegenbaur, the anterior inferior root (Va) of Jackson and 

 Clarke, and the anterior root (i) of Balfour." 



" ip) A posterior, larger ganglionic root, the ventral or sec- 

 ondary root (V /3) " = " anterior part of the second root of 

 Stannius, the ventral division (/3) of the posterior root {b) of the 

 the fifth of Gegenbaur ; apparently the inferior rootlet of the 

 second root (V /3), and possibly part of the third root (V 7 and 

 VII) as well, of Jackson and Clarke ; the second root (2) of the 

 fifth of Balfour." 



" The seventh nerve in the adult arises by two roots : {a) A 

 dorsal root arising far up the side of the medulla, at the 

 junction of the thickened sides and thin roof of the fourth 

 ventricle" ("primary" root of VII, VII a). "This root is the 

 third or dorsal root of Stannius ; the dorsal rootlet (a) of the 

 posterior trunk ib) of the fifth of Gegenbaur ; the superior 

 rootlet of the second root (V/3) of Jackson and Clarke, and 

 the dorsal and posterior root (3) of the fifth of Balfour." 



" (b) A ventral root arising from the side of the medulla at a 

 rather lower level than the posterior root of the fifth" ("second- 

 ary" root of VII, VII ^). In the adult it comes to lie in close 

 contact with the secondary root of the fifth. " This root is the 

 posterior part of the second root of Stannius, the root of the 

 seventh of Gegenbaur ; part, or possibly the whole of the third 

 root (V7 and VII) of Jackson and Clarke ; and the single root 

 of the seventh of Balfour." 



These investigators first showed that the R. buccalis belongs 

 to the VII. Their homologies do not appear to me, however, 

 to be entirely correct. Their second posterior ganglionated 

 root (b) of the V is plainly the sensory root of the Trigeminus 

 proper. As such, it corresponds, together with the motor root- 



