KUTCHIN. — PERIPHERAL NERVOUS SYSTEM OF AMPHIOXUS. 603 



cations in the distribution of the visceral nerves of Amphioxus. The 

 investigations up to the present time estabhsh the fact that the visceral 

 rami of the dorsal nerves are elaboratel;)' connected throughout the 

 atrial region, and that multipolar nerve cells occur in connection with 

 these visceral nerves. 



E. Nerves Posterior to the Atriopore. 



Dogiel ( : 02) has described in detail the main cutaneous branches 

 of these nerves, and illustrates the larger branches in his Figures 2 and 

 3. He notes the presence of "rami communicantes " connecting 

 two adjacent ventral rami of dorsal nerves in their course over th« 

 side muscles of this region, but does not limit the occurrence of such 

 connecting branches to the posterior portion of the body. 



In the specimens which I have ol)served, the cutaneous branches 

 in this region are more numerous than represented by previous authors. 

 Rich plexuses are frequently present both between the dorsal rami and 

 between the \'entral rami of these nerves on the same side of the body 

 (PL 6, Figs. 34 -3()). These plexuses will be described in connection 

 with the sensory nerve endings. A "ramus communicans" was 

 frequently found in this region, as well as in other parts of the body. 

 The elaborate branching of the last dorsal nerve of Branchiostoma 

 caribaeum is illustrated in Figures 31 and 33 for the right and left sides 

 respectively. This pair of nerves is exclusively cutaneous, and its 

 branches are more numerous than the figures by previous authors 

 indicate. The most posterior dorsal nerve is posterior to the last ven- 

 tral root, and, according to Hatschek's interpretation of the relation of 

 the nerves to the myomeres, belongs to the preceding myomere. He 

 states that each dorsal nerve belongs to the myomere anterior to the 

 myoseptum through which it passes, and that the ventral root in- 

 nervating this myomere appertains to this dorsal root. 



Little attention has been previously given to visceral branches in 

 this region. Heymans et van der Stricht ('98, p. 43) note in Golgi 

 preparations apparent nerve fibers on both the parietal and visceral 

 mucosa faces posterior to the abdominal pore. They were unable to 

 find the origin of these nerves, or to trace their course, but suggest 

 that they may come from the " abdominal" visceral nerves (Hatschek), 

 or, more probably, as an extension of "thoracic" longitudinal nerves 

 into the "abdominal" cavity. These authors seem to apply the term 

 "abdomen" to the region containing the intestinal canal. They also 

 note in Golgi preparations nerve fibers supplying the surface of the 



