ANATOMY AND METAMORPHOSIS OF CYCLOPS. 225 



larger, pear-shaped, segmented ceplialoihorax, and a nar- 

 row segmented abdomen, which is forked posteriorly and 

 ends in two bunches of long hairs, which make up a little 

 more than half the total length of the abdomen. 



a. The cephalotliorax. This is made up of an anterior 

 unsegmented carapace, which is followed by a number of 

 free thoracic somites. 



1. The carapace (Fig. 118, d) is broad and a little 

 longer than wide, and forms about a third of the entire 

 length of the animal. Its anterior margin is rounded at 

 the sides, but the even curve is a little* broken on the 

 anterior median line, which is occupied by a short rounded 

 rostrum. 



(i.) Upon the base of the rostrum, in the median line 

 of the body, note the single dark brown eye-spot (b). A 

 higher power shows that this is formed by the fusion of a 

 pair of eyes, and the two lenses may be seen upon the 

 sides of the spot. 



(ii.) Projecting from below the sides of the rostrum 

 are the. large, many-jointed first antennas (a), which bend 

 backwards along the margins of the carapace, and carry a 

 number of scattered hairs upon their anterior edges. 



(iii.) Beside and below these are the shorter jointed 

 second antennae. 



2. Posterior to the carapace the dorsal surface of the 

 cephalotliorax is formed by the movable terge of the four 

 free thoracic somites (e, f, g, h) . These are of about equal 

 length, but they gradually decrease in width from before 

 backward ; the first being nearly as wide as the carapace, 

 and the fourth only about half as wide. 



b. Back of the last thoracic somite is the narrow, 

 slightly tapering abdomen, divided into four apparent 

 segments. 



