CLADOCERA. 



279 



The highest members of the group of sucking Entomo- 



stnica are Cdligus and Argulus, in which the body is seg- 

 mented, with antenna and free 



mouth-parts and legs ; the latter 



genus with compound eyes. Cali- 



gus curt u * M tiller lives on the cod, 



and Argulus alosce Gould on the 



alewife. 



Order 3. Brancliiopoda. - - This 



order includes such Crustacea as I 



in the higher forms breathe by I 



rather broad feet. There is a con- 

 siderable range of 

 form from the 

 Ostracoda, repre- 

 sented by Cypri*, 



in which the feet Fig 235 ._ Actheres of the trout 

 are much as in Cy- 

 clops, through Daplinia and Sida (Fig 237) 

 which represent the Cladocera, up to the 

 Phyllopods. The suborder of Ostracoda 

 (Cypris) arebivalved, the shell often thick. 

 They have two eyes, two pairs of antennae, 

 a pair of mandibles with a jointed feeler 

 (palpus) and a gill, and four pairs of feet, 

 the second pair often carrying a small gill. 

 The shells of certain species allied to Cyprlx 

 abound in the lowest Silurian strata. The 

 species live in fresh-water pools and in the 

 ocean at various depths. They undergo no 

 metamorphosis, the youngest stage being a 

 shelled Nauplius. 



The suborder Cladocera is represented by 

 fresh and salt-water species. The higher 

 forms are Sida and Daplinia. They are 

 called water-fleas from their jerky motions. 

 The eggs of Daplinia are borne about by 

 sac. Peneiia of the females in so-called brood-cavities on 



the sword-fish, female. the back under the ghell> There are twQ 



sorts of eggs, i. e., the "summer" eggs, which are laid by 



