FBESH-WATEE CEUSTACBANS. 



293 



like an "Indian club," or an elongated pear, and it is quite 

 large enougk to be easily seen without the help of a noagnif ying- 

 glass. It has received the generic nanae of Cyclops, from 

 the fact that it possesses only one eye, which is situated in 

 the centre of the fore-part of the first and largest segment 

 of its body ; while the specific na,me of guadricornis (" four- 

 homed") has been giyen to it on accoimt of what may be 

 called its double antennae. The male Cyclops differs from 

 the female in the formation of its antennae. The superior or 

 upper anteimsB of the latter are long, tapering, and gracefully 

 curved, while those of the former are rather shorter and 

 thicker, and slightly swollen 

 near their tips, which termi- 

 nate ia a kind of hinge-joint. 

 The lower pair of antennae 

 of both the male and female 

 are not nearly so long or so 

 slender as their upper pair. 

 All the anteimBB have numer- 

 ous articulations, and are 

 fringed with very fine fila- 

 ments. Cyclops possess five 

 pairs of legs, two pairs of 

 foot-jaws, and at the end of 

 their bodies two elongated 

 lobes, to each of which are 



attached four set» of difEerent lengths; these setae, Uke the 

 antennae, are also finely and beautifuUy fringed. The females 

 are about three times as numerous as the males, and may very 

 frequently be seen swimming about with their eggs hanging 

 to each side of the lower part of their bodies. The eggs 

 can easUy be detected with the naked eye, but under the 

 microscope they look very like bunches of grapes. In each 

 cluster there are sometimes as many as thirty or foi-ty eggs. 

 M. Jurine is said to have made careful observations and 

 calculations in regard to the increase of these Entomostraca, 

 and he came to the conclusion that one female would lay, or 

 rather produce, her eggs at least eight times within three 



Fig. 169. Cyclops quadricornis 



(a, MUCH ENLARGED ; b, NATURAL SIZE). 



