604 proce?:ding.s of the American academy. 



intestine, and (p. 44) branches from certain dorsal nerves (14th to 

 16th from the tail end) of the left side of the body supplying the anus. 

 A branch from the right 13th (from the tail end) appears to have the 

 same destination. Dogiel ( : 02) states that the dorsal ner\-e pairs 

 from XL, or XLI, to LIII, or hlX, inclusive, give off ascending 

 visceral branches, which bend around the ventral border of the side 

 muscles, or penetrate a myoseptum to reach the interior. Beginning 

 with ner\'e XLI or XLIT, these visceral branches di\'ide into a great 

 number of branchlets, which weave around the whole rectum reaching 

 to the anus. A fine plexus is formed in the w^alls of the anus from 

 exceedingly fine and slightly varicose branches of nerves LI, LII and 

 LIII. Dogiel does not state that the nerves of one side are more 

 concerned in the innervation of the anus than those of the other. It 

 is uncertain whether or not he finds ^'isceral branches from the nerves 

 succeeding nerve LR"; his figures surely do not illustrate such branches. 

 His Figures 19a and 1% show ramifications of the visceral branches 

 of nerves XLII to XL VI inclusiAC. These extend on the inner surface 

 of the side muscles from their A'entral Ijorder a short distance dorsad. 

 Both figures are drawn as seen from the exterior. 



In the specimens I have examined, occasionally visceral branches 

 were apparently lacking to certain dorsal nerves, but, as Dogiel has 

 observed, the manner in which these penetrate to the interior may be 

 such that a A'iew from the exterior fails to give any e\'idence of their 

 presence. Examination of a large number of specimens disclosed 

 visceral branches to practically all the ner\es of this region from XL 

 to LXI, inclusive. However, visceral branches could ncAer be dis- 

 cerned from the exterior for all of these nerves in a single specimen. 

 In one case nearly all dorsal nerves as far as nerve LX showed visceral 

 branches. I have never observed visceral branches in connection 

 with nerves LXII, LXIII or LXIV (when 64 nerves are present). 

 The inner-vation of the anus, which. lies on the left side, is usually 

 supplied by branches of lift nerves LI-LI 1 1, in both species. Varia- 

 tion occurs here, and it is probable that in Branchiostoma caribaeum 

 more anterior nerves may occasionally innervate this structure. 

 Frequently only two of the nerves mentioned above give off branches 

 which weave about the anus. Right nerves LI, LII and LIII often 

 show branches penetrating to the interior, but these could never be 

 traced to the anus. 



In methylene-blue preparations suitable for dissection, the intestine 

 is rarely in favorable condition for study, although the main visceral 

 nerve branches impregnate particularly well. Such preparations cut 



