314 'Journal of Comparative Neurology and Psychology. 



dorsal cornua. The dorsal root of the first spinal nerve, which 

 terminates in the first lobe, is, however, not greatly enlarged. The 

 prime motive, then, for the development of this lobe is not the 

 modification of the pectoral fin, but, rather to serve as the terminal 

 nucleus of the spinal Vtract, which is of very great size inPrionotus. 

 In this fish the spinal V nucleus is a direct derivative of the dorsal 

 cornu. The funicular nucleus is not closely related to the dorsal 

 cornu (the grey matter of the "lobes"), but rather with the ad- 

 jacent formatio reticularis. In both of these respects Prionotus 

 agrees very closely with the morphological relations in Ameiurus 

 (Herrick '06), although the structural details are very different. 

 The spinal V tract, as in other fishes, can be separately followed 

 by reason of the heavier medullation of its fibers, into the spinal 

 cord beyond the first spinal nerve, a remnant of it being recognized 

 in Fig. 9. 



As we pass forward into the oblongata from the funicular nucleus 

 region, the first accessory lobe (dorsal cornu + nucleus of spinal V 

 tract) disappears before the funicular nucleus, and the latter is 

 enveloped dorsally by the spinal V tract, laterally by the dorso- 

 lateral fasciculus and ventrally by the latter tract and massive 

 bundles of the formatio reticularis alba, which farther forward 

 become incorporated into the dorso-lateral fasciculus (Fig. 11). 

 When the level of the vagal lobe is reached the funicular nucleus 

 has entirely disappeared, its place being occupied by a very small 

 substantia gelatinosa Rolandi. Here the spinal V tract receives 

 a strong accession of descending fibers from the general cutaneous 

 root of the vagus (Fig. 12), and there is added to the dorso-lateral 

 fiber complex on its ventral side the ascending secondary gus- 

 tatory tract from the vagal lobe. Whether there is a descending 

 secondary gusatory tract from the vagal lobe represented in the 

 fasciculus lateralis my preparations do not enable me to state. I 

 find no clear evidence of it. Secondary vagus fibers clearly pass 

 in large numbers to the formatio reticularis of the same side and 

 others cross as internal arcuate fibers in the ventral commissure 

 (Fig. 12). These are of fine caliber, like the other secondary 

 vagus fibers, and can therefore be distinguished from the other 

 and coarser fibers of this commissure which are derived from the 

 substantia gelatinosa and tuberculum acusticum and belong to 

 the secondary somatic sensory system. They arise from the whole 

 extent of the vagal lobe, which is not obviously differentiated into 



