NERVOUS SYSTEM OF PELAGIC XEMERTEANS. 



133 



either at the attachment of the proboscis or in the organ im- 

 mediately posterior to its insertion. But in other forms, where 

 the proboscis is inserted close in front of the brain, the proboscidial 

 nerves either arise in the complete number from the ventral brain 

 lobes and the commissure adjacent or branch immediately after 

 their origin. 



bm 



Im' 



cm 



dvm 



FIG. 9. Diagram of portion of horizontal section of tentacle and adjacent 

 body wall of Ncctoncmcrtcs mirabilis Verrill, showing the four large 

 tentacular nerves originating from the lateral nerve cord (In). These are 

 homologous with the lateral peripheral nerves (//>) of the rest of the 

 body; bm, basement layer underlying the surface epithelium; Itn, longi- 

 tudinal and cm. circular muscular layer; ilm, internal longitudinal muscles; 

 drm, dorsoventral muscles; par, parenchyma. 



