20 Journal of Comparative Neurology. 



easily recognized and its development though great is not ex- 

 cessive (Fig. 14.). It soon assumes a dorsal position in the 

 oblongata and the Xth nerve arises from it in two main divis- 

 ions, both passing dorsad of the spinal Vth bract. Cephalad of 

 the Xth the acusticum soon begins upon the side of the ob- 

 longata and at the caudal end of the fused preauditory portion 

 of the fasciculus communis systems, the cerebellar crest appears. 

 Two isolated fasciculus communis roots enter, one a short dis- 

 tance cephalad of the mass of the Xth nerve, the other (IX ?) 

 near the level of the entrance of the lateral line nerve (VIII 

 post., Mayser). The tubcrculum impar is a single mass, al- 

 though a mesal groove on its dorsal side indicates its paired 

 composition. From it fibers concentrate to form Vllaa which 

 continues cephalad for a short distance as a round bundle after 

 the tuberculum impar has been replaced by the fused acusti- 

 cums. The roots in this region are much as in other forms and 

 as described by Mayser, except that he recognized no root 

 from the " tuberculum" acusticum except the Vlllth ; Vllb and 

 Vllaa as before, emerge together, Vllaa cephalad, Vllb cau- 

 dad. The point of interest in Notemigomis is that the pre- and 

 postauditory portions of the fasciculus communis system are 

 directly continuous as in the teleosts before described and the 

 postauditory or vagal portion does not overlap the tuberculum 

 impar. The caudal limit of the communis fusion and the cere- 

 bellar crest upon the acusticum is nearly the same. 



In Notropis, the common shiner, the vagal lobes are some- 

 what more developed and extend cephalad slightly around the 

 tuberculum impar, so that in the same transection there is in- 

 cluded the tuberculum impar, lobus vagi, and acusticum. In 

 Exoglossum this is yet more marked and the structure is more 

 carp-like (Fig. 26). The Xth as before, passes dorsad of the 

 spinal Vth, occasionally breaking through it. An isolated ceph- 

 alic fasciculus communis root (IX?) enters caudad of the en- 

 trance of the lateral line nerve. 



In the carp the development and eversion of the vagal 

 lobes (postauditory portion of the fasciculus communis) is much 

 greater so that the spinal Vth is ventral rather than lateral and, 



