ZooL.— Vol. III.] HEATH— EPIDELLA SQUAMULA. 1 29 



In the spaces formed by these commissures and the longi- 

 tudinal nerves is an anastomosing system of delicate fibers 

 which originate at irregular intervals along the larger cords. 

 The nerves extending outward from the outer pair of longi- 

 tudinal cords also break up into a complex network which 

 extends to the margin of the body. In some cases nerves 

 from some of these smaller branches appear to terminate 

 close to the surface in a number of excessively fine branches 

 beset with indistinctly marked varicosities. The greater 

 number, however, give off short branches which attach to 

 the numerous muscle fibers lying close to the surface of the 

 body. 



As noted above, the dorsal pair of nerves arises on each 

 side of the pharynx at the point of origin of the ventral 

 longitudinal cords. From here they pass to the dorsal side, 

 and lying just beneath the superficial musculature, extend 

 the length of the body. Their course throughout is almost 

 parallel, which accordingly brings them closer together than 

 the inner ventral pair. In the most favorably preserved and 

 stained preparations they may be traced to a point on each 

 side of the ovary, where they apparently end. In speci- 

 mens treated with methylen blue, however, they are found 

 to continue to the end of the body, and to give rise to a 

 system of nerves which is but little less extensive than that 

 of the ventral side. At frequent intervals commissures 

 arise, and toward the outside numerous«nerves are given off 

 which soon branch, forming a plexus whose meshes grow 

 smaller and smaller as the margin of the body is approached. 



Along the path of some of these nerves bipolar cells are 

 occasionally found, but they are of comparatively rare 

 occurrence. Situated a short distance from each longitudi- 

 nal cord, usually to the outside, are at least twenty multi- 

 polar cells of relatively large size, which are relatively more 

 abundant in the anterior half of the body. With methylen 

 blue these cells stain intensely, and some of the fibers pass- 

 ing off from them often have a coarse irregular appearance 

 when compared with the smooth delicate nerves in other 

 parts of the body. In many instances, four or five nerve 



