PLATE 6. 



All figures are from methyl ene-blue preparations. 



Figure 31. Branchiostoma caribaeum. The same individual as that shown 

 in Figure 33. The nerves of the posterior end, on the right 

 side of the body. X 93. 



Figure 32. B. lanceolatum. The interior surface of the ventral fin and side 

 muscles bordering upon it, from the region between the 

 atriopore and the anus. Posterior is vip. The branches from 

 the ventral rami of dorsal nerves which reach the interior are 

 marked a, a, a. The branch ai, bends toward the exterior. 

 Part of a membrane, somewhat detached from the side muscles, 

 is indicated at b. The bilateral asymmetry of the muscle 

 segments is illustrated. X 84. 



Figure 33. B. caribaeum. Nerves of the posterior end of the body, on the 

 left side. The epithelium of the skin is not present. The 

 end of the notochord is bent in the same manner as the termi- 

 nal ampulla of the neural tube. X 93. 



Figure 34. B. lanceolatum. Cutaneous plexuses between right dorsal 

 nerves XLVI, XLVH and XLVIII, in the region of the side 

 muscles. The coarser, deeper pleXus is marked pi (center of 

 figure), the finer, more superficial one po (upper left quarter 

 of figure). A cell-like structure is shown at c, in connection 

 with cutaneous nerve fibers and at a, a nerve passing through 

 myoseptum to inner face of muscle. X 41. 



Figure 35. B. lanceolatum. Cutaneous plexuses between right dorsal 

 nerves LIII and LIV, and between LV and LVI, in the region 

 of the side muscles. The letters correspond to those of 

 Figure 34. The branch at .i- joins nerve LVII. X 41. 



Figure 36. B. lanceolatum. Cutaneous plexuses between right dorsal 

 nerves LIV and LV, in the region of the side muscles. The 

 letters correspond to those of Figure 34. X 84. 



