200 



Arthropoda. Class 1. Crustacea. 



Order f). Copepoda. 



The order Copepoda comprises a large number of free-living 

 forms, and also a multitude of parasites, wliicli conform, on the whole, 

 to the same type, although they are often considerably modified in 

 accordance with their peculiar mode of life. 



The free-living Copepods will be first considered. The body 

 is divided into three regions, cephalothorax, thorax, and 

 abdomen. On the cephalothorax there is a nauplius- 

 eye, consisting of two, three, or more ocelli, and attaining a 

 considerable size in some pelagic forms ; lateral eyes, on the 

 other hand, are always wanting. The cephalothorax bears, 

 further, two pairs of antennae, both of which are well- 

 developed. The anterior antennse are usually the longer, 



Fig. 163. Cy clops, a nauplius, h—d later stages of development, e adult animal 

 (only the left mandible and maxilliped, and the right maxiUas are figured) : enlarged. 



and serve as natatory organs ; in the males they are frequently 

 used also for holding the female during copulation; they are then 

 bent in the middle, and the distal can close upon the proximal part. 

 The mandibles are usually provided with palps, the palp often 

 possesses a small exopod (Fig. 151 D). Behind the mandibles 

 are the two pairs of m axil lee and a pair of maxilliped s. 



