NO. 2063. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 



593 



First copepodid or free-swimming stage. — Body elongated, flattened 

 dorso-ventrally and made up of a cephalothorax, three free thorax 

 segments, and a fused gen- 

 ital segment and abdomen, 

 carrying the anal laminae. 

 The cephalothorax is a more 

 (Clavella) or less (Ach- 

 theres and Sdlmincola) com- 

 plete fusion of the head and 

 first thorax segment. In the 

 latter genera the separation 

 of the two is indicated by 

 notches on the lateral mar- 

 gins and by a dorsal groove; 

 in the former genus these do 

 not appear. The shape of 

 this cephalothorax is elhpti- 

 cal in Salmincola, ovate in 

 Clavella, and eUiptical or sub- 

 qu adrilateral in AcTitheres. A 

 characteristic copepod eye is 

 found at about the center of 

 the cephalothorax in Clavella 

 and Salmincola. The eye in 

 Aclitheres is so rudimentary 

 that it can not be seen except 

 in sections. In the front of 

 the head, close to the dorsal 

 surface, Hes the attachment 

 filament which is characteris- 

 tic of this family. It con- 

 sists of a long cyhndrical rod, 

 enlarged at either end; the 

 enlargement of the distal end 

 is in the shape of a mushroom 

 or umbrella, and is the part 

 that sticks to the flesh of the 

 host, and becomes the bulla 



or attachment organ of the adult parasite. The cyhndrical rod is 

 folded in a single loop in Salmincola, coiled like a rope in Aclitheres, 

 and wound into a tight spiral in Clavella (fig. 13). 



The first thorax segment is two-thirds as large as the head, is fused 



with the latter, and tapers posteriorly, terminating in two large lobes 



which correspond to the posterior lobes of the carapace in the Caligidae. 



The second (first free) thorax segment is much larger than the seg- 



34843 ° — Proc.N. M. vol.47— 14 38 



O^mm. 



Fig. 13.— Copepodid labv.v of Clavella uncinata. 



