No. I.] THE CRANIAL NERVES OF AMPHIBIA. 113 



the dorsal VII emerge from the medulla together and only 

 become separated later in their course. An interesting question 

 here arises. Does the Acusticus in its extension dorsad ap- 

 propriate a portion of the dorsal VII t This could best be 

 determined by a careful study of these nerves and their internal 

 origin through the stages of transformation into the frog. If 

 such a transference takes place it would lead to the remark- 

 able result that the Acusticus of the Urodela is not strictly 

 homologous with that of Anura. It should also then be 

 determined what structures in the ear receive this increased 

 nerve supply. Some further aspects of this question will be 

 dealt with later. 



The exit of the VII + VIII (899-876) occupies a large 

 portion of the side of the medulla. In the most caudad part 

 of this exit there may be seen fibres leaving the medulla 

 which, when traced internally, curve ventrad, and evidently 

 have an origin much inferior to that of the bulk of the VIII. 

 This root has been observed by Stieda (59) and others, and is 

 spoken of in Ecker and Wiedersheim's Anatomy of the Frog, 

 (17) as derived from the motor trigeminal nucleus. Osborn 

 (45), however, has demonstrated that a similar ventral rootlet 

 in Cryptobranchus is derived directly from the posterior longi- 

 tudinal fasciculus. My sections, being of smaller brains, are 

 inadequate for the settlement of the derivation of this root in 

 the tadpole. I think it probable that some of the fibres origi- 

 nate from a portion of the trigeminal motor nucleus, and 

 possibly others may come from the posterior longitudinal 

 fasciculus. I have so indicated them in the chart. 



These fibres, as they emerge from the medulla, form a 

 bundle close under the large root of the Acusticus. This 

 bundle was termed, in the abstract in the Zoologischer Anzeiger 

 (61), the " ventral root of the ventral VI I" or '' VII ab.'' 



Slightly cephalad of this, and between it and the Acusticus, 

 another root can be distinguished, composed of fine fibres, 

 which are derived from a bundle representing the fasciculus 

 communis of Osborn (PI. XI, Fig. 39). This was designated 

 " VII aa'' in the Anzeiger abstract. It fuses with the first 

 root and these two ventral roots of the VII were, for con- 



