AMERICAN PARASITIC A RGULID.^- WILSON. 



693 



From each of the other ganglia is given off a pair of nerves (two 

 pairs in coregoni) which run diagonally backward and innervate the 

 swimming legs in order. From the posterior ganglion two pairs of 

 nerves in the American species and foUaceus, and three in coregom, 

 run directly backward along the ventral wall of the intestine. The 

 outer of these two pairs goes to the posterior swimming legs; the 

 inner one runs into the abdomen and innervates its muscles, together 

 with those of the heart. Especially worthy of notice are the innerva- 



FiG. 21.— Female sexual organs of Argulus amertcanus. o., Ovary; ov., oviduct; .t. p., semen 

 papilla; i. r., semen receptacle; t.p., tactile papilla at the opening of the oviduct. 



tions of the basal lobes of the posterior swmiming legs, which are used 

 as tactile organs in ^^g laying, as already described, the innervation of 

 the accessory sexual organs on the swimming legs in the male, and 

 that of the tactile papillw on either side of the opening of the oviduct 

 in the female. 



For sense organs the Arguli possess only eyes and tactile organs. 

 The eyes are large in most species and are made up of 30 to 60 facets, 

 spherical or ellipsoidal in form, but packed so closely together as to 

 become more or less angular. The outer portions of these facets are 

 free from pigment, but the inner portions are heavily pigmented. 



