NERVOUS SYSTEM OF PELAGIC NEMERTEANS. 



dorsal nerve inward through the circular muscular layer and 

 thence laterally between the two muscular layers of the body- 

 walls. These nerves appear to constitute part of a great plexus 



cm 



cm- 

 bm 



FIG. 7. Diagram of portion of transverse section of body of Pelagone- 

 meries joubini Coe, immediately posterior to the 'brain, showing origin of 

 the nerve cord muscles (ncm, ncm) from the outer spiral musculature 

 of the proboscis sheath, and the three main branches, dorsal (dpn), lateral 

 (Ipn), and ventral (vpn) which leave the nerve cord in each interdiverticular 

 space ; re, rhynchocoel ; plm and pent, longitudinal and circular-spiral muscu- 

 lar layers of proboscis sheath ; other lettering as in Fig. 2. 



of nerve-fibers which extends between the circular and longi- 

 tudinal musculatures throughout the length of the body, both 



