CYCLOPID^l. 187 



arise from the upper portion of the segment, on each side 

 of the eye ; they are always larger than the inferior pair, 

 and are generally composed of numerous articulations, 

 which are plentifully supplied with short setae. 



The male is distinguished by a peculiarity in the an- 

 tennae which at once marks the sex. Most frequently 

 they are shorter and thicker than in the female, and either 

 one (the right one as in Diaptomus Castor) or both (as in 

 Cyclops quadricornis, &c.) have a swelling near the centre, 

 or towards the extremity, followed by a moveable joint, 

 which acts like a hinge, and which serves a very useful 

 purpose in the act of copulation. The inferior antennae, 

 or antennules, are situate immediately beneath the pre- 

 ceding, and are composed of fewer articulations. Both 

 of these organs are made use of by the animal to assist 

 itself in progressive motion. Immediately below the an- 

 tennules is situate the mouth, in which we find a labrum 

 or lip, and the mandibles : these latter organs may be de- 

 scribed as consisting of three parts, body, neck,* and 

 palpiform branch, but differing from each other in several 

 respects in the various genera. Beneath these, again, are 

 situate the jaws, which are almost obsolete in this family. 



Below the mandibles are situate the foot-jaws, which 

 Jurine calls hands ; a term which Muller had already ap- 

 plied to the same organs in one marine species he describes, 

 the Cyclops chelifer.^ These organs are always situate 

 in the same place, but all differ from each other in so 

 many respects that it will be necessary to describe them 

 in the species of each genus separately. The use of these 

 organs, according to Jurine, is to push constantly towards 

 the mouth a current of water, carrvino; along with it the 



/ O O 



particles destined for the animal's food. Immediately 

 beneath the foot-jaws are situate the first pair of feet. 

 They are double, consisting of two stalks arising from a 

 common base, each stalk consisting generally of from two 

 to four articulations, more or less furnished with setae, 



* Prolongation of Jurmc. f Entoino.it., p. Hi. 



