12 Journal of Comparative Neurology. 



where. This conclusion is supported by the following consid- 

 erations. The root is larger than the condition of the eyes 

 would lead us to expect. The nucleus from which it arises is 

 universally devoted to viscero-motor nerves, while VI is somatic. 

 Finally, this root is lateral while the VI root is ventral in all 

 other forms. The only suggestion which the writer can make 

 is that the equivalent of VI is found in the bundle of coarse 

 fibers in V which arise from the ventral motor column in the 

 region of VII and VIII. This isolated portion of the ventral 

 motor column occupies the same position as the nucleus of VI 

 in Acipenser. I hope to reinvestigate this interesting point on 

 more suitable preparations. 



I have been unable to trace the IV nerve to its cells of 

 origin. It is very small (Fig. 13). 



As described by Ahlbokn, the nucleus of III is in two 

 parts (Fig. 24). The roots decussate beneath the aqueduct 

 but not all the fibers cross. One portion of the nucleus of 

 origin lies at either side of the median line beneath the aque- 

 duct and most or all of the fibers arising from it decussate. 

 This is a compact mass of cells lying rostral to the root bun- 

 dles, while immediately caudal to the roots a similar mass of 

 cells constitutes the end-nucleus of the bundles of Meynekt. 

 The other portion of the nucleus consists of larger, spindle- 

 shaped cells which lie close around the root at its exit, the 

 greater number of cells being massed on the cephalic surface of 

 the root. Some of the cells project beyond the general con- 

 tour of the brain with the issuing root. The fibers of these 

 cells are said by Ahlborn to cross to the opposite side, with 

 few exceptions. The opposite is the case, since many fibers 

 are readily traced into the nerve of the same side while I have 

 been unable to trace any to the opposite side. 



b. The Miillerian fibers. 



Ahlborn has described the Mullerian fibers in three 

 bundles, a lateral uncrossed, a median crossed, and a median 

 uncrossed. The lateral uncrossed and median crossed bundles 

 arise from the spindle cells situated among the fibers of the 

 VIII roots. Each of these cells sends a peripheral process out 



