HARD WICKE ' S S CIE NCE-GO SSI P. 



85 



and tapering, while those of the male are shorter, 

 thicker, and clublied at extremity. The female, also, 

 bears (except during a part of winter) large external 

 egg-sacs, each containing from thirty to forty ova. 



that it was long thought to be a distinct species. 

 Almost as prodigiously prolific as the Cyclopidse 

 are the merry little water-tleas (Daphniadse). 

 There are at least seven known British species, of 





Fig. 63. — Cypris ornata [magnified). 



Fig. isz.—Daphnia pnlex (female). The small 

 figure within the ring shows the nat. size. 



Fig. 64. — Freshwater Ssknm^ fCnnnitaiiis f-iile.v). 

 b. Head oi G. pulex. 



Fig. 62. — Aselhis aqnatkjis. The line between the figures 

 indicates the nat. size, a, upper side ; b, under side. 



These do not become larger while in the sac, but 

 they alter in colour until, in from two to ten days, 

 according to temperature, &c., the queer-looking 

 young Cyclops issues forth so totally unlike its parent 



which Daphnia piikx is the commonest, and is to be 

 taken all the year round. Sometimes pulcx is seere 

 in horse-ponds, &c., in such multitudes that it forms a 

 rust-red cloud which moves about in the water, guided 



