THE BRANCHIOPODA. 



249 



the head or the thorax, the segments of the latter being en- 

 tirely free, while the former is similar in shape to that of an 

 Insect, or Edriophthalmous Crustacean, and carries two large 

 stalked eyes, two antennules (singularly modified in the 

 male), two antennae, a pair of mandibles, and two pairs of 

 iiuixillip. 



In Esther ia and Limnetis, the males are met with in full 

 proportion to, and may be even more numerous than, the 

 fem;iles. No males are known in Lirnnadia gigaB^ although 

 thousands have been examined, while, in L. >'" A >/ana, 

 more males than females have been found. In Sranchipus^ 

 males are fewer than females ; in Artemia, they occur only 

 at rare intervals. In Daphnia, the males are few, and appear 



FIG. tt.-Limne.tis brachyurus (after Grnbe).-The upper left-hand flgure is the 

 male, the other the female; one valve of the eir ipaee in eneli ease IVMMLT n-mored. 

 A 1 , Antenn tiles. 4, Antennae. A, Yonnp larva. R. The nn\<- further advanced. 

 c, head ; o, eye ; d. carapace : <*, body. A '. Antennae. Jf. Mandible*, d', grett 

 plate (labrum ?) which covers the mouth. 



only at certain seasons of the year. But notwithstanding 

 tho rarity or absence of the malos in many of these genera, 

 reproduction proceeds with irnnt npiditv.' The >\a are capa- 

 ble of development without fecundation ; and isolated females 



