CYCL0PIDJ3. 
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, carrying along with it the 
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 Jurine. 
f Entomost., p. 114. 
