692 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



The ventral chain consists of six ganglia placed so near together 

 that they are almost completely fused. But they can still be distin- 

 guished clearly by the transverse grooves and constrictions between 

 them (tig. 20). They diminish in size from in front backward, the 

 anterior one being about twice the diameter of the posterior. From the 

 anterior ganglion a stout nerve (there are several others leading from 



Fig. 20.— Thk nervous system of Akgulus americanu.s. 



the same ganglion in coregoni according to Clauses ligure) is given off 

 on either side which divides quickly, the anterior branch innervating 

 the mouth parts, while the posterior branch passes out into the cara- 

 pace. Another stout nerve is given off usually from the second gan- 

 glion^ which divides and innervates the two pairs of maxillipeds. 



' Leydig states that this nerve comes from the first ganghon in foliaceus. Claus 

 gives it from the second ganghon in coregoni, an arrangement which exists, also in 

 aDwricauus and reratcolor. It has not yet been located in other species. 



