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WESLEY R. COE. 



dorsally and ventrally (Fig-. 4). The plexus is in frequent com- 

 munication with the peripheral nerves from the lateral cords, as 

 well as with the dorsal and dorsolateral nerves. 



Tentacular nerves. The adult males of Ncctonemertes and 

 both sexes of Balfcnanctncrtcs are each provided with a pair of 

 tentacles immediately back of the head. These appendages are 

 lateral outgrowth of the body walls and are supplied with large 

 nerves homologous with the lateral peripheral nerves in other 

 parts of the body (Fig. 9). 



Proboscis-sheath nerves. In many pelagic species the proboscis 

 sheath is supplied with nerves which enter it at the ring where 

 the proboscis is attached, but in other forms the organ also receives 

 one or more pairs of fine branches from the dorsal peripheral 

 nerves (Figs. 2, 7). 



ncm 



ncm 



FIG. 8. A, Transverse section of lateral nerve cord and accompanying 

 muscle (ncm) in Cunconemcrtcs gracilis Coe. B, Same in Balananemertcs 

 chuni Burger. C, Section of lateral nerve cord in Planktoncmertes agas- 

 sizii Woodworth, showing the origin of dorsal lateral and ventral periph- 

 eral nerves. 



Proboscidial nerves. The proboscis is large and highly spe- 

 cialized in most of the pelagic nemerteans, with a powerful mus- 

 culature and a thick epithelial lining of secretary and sensory 

 cells in addition to the minute sickel-shaped weapon with which 

 it is provided. Consequently it requires an abundant supply of 

 nerves. In some forms these are provided by means of a pair 

 of large nerve stems arising from the points where the ventral 

 commissure joins the ventral brain lobes (Fig. i). This pair of 

 large nerves divides into the definite number of proboscidial nerves 



