526 



ZOOLOGY 



SECT. 



There is considerable diversity of form among the Eupliyllopoda. 

 Apus has already been described. Branchipus (Fig. 413, 1) and 

 Artemia (the Brine-shrimp), are small shrimp-like forms, the 

 former living in fresh-water lakes, the latter in brine-pools ; they 

 have no carapace, and the eyes are raised on unjointed stalks. In 

 Limnetis (2), on the other hand, the carapace is large enough to 

 cover the whole body, and in Estheria (3) it takes the form of a 

 shell t formed of two parts or valves, united by a hinge, and resem- 

 bling the shell of a cockle or other bivalved mollusc. The limbs 



anil 



ov 



1. Branchipus 



ant. 2 



3. E sl-heri a 



FIG. 413. Three Euphyllopoda. In 3, a is the shell, I the animal with one valve of the shell 

 removed ; anft. antennule ; ant 2 , antenna ; ht. heart ; m. adductor muscle ; md. mandible ; 

 or. f ovary _, a. unpaired process from head ; p, copulatory appendages ; sh.gl. shell-gland ; 

 t. testis. (After Gerstaecker.) 



have the same general structure as those of Apus, but the 

 antennae are often of considerable size, and are sometimes modified 

 into prehensile organs. 



In the Cladoccra, of which the common fresh-water Daphnia 

 (Fig. 414, 1) is a good example, there is a great reduction in size 

 (1-2 mm.), and a corresponding shortening of the body, by a 

 reduction in the number of metameres. Segmentation is very 

 imperfect, and the whole body is covered by a large folded 

 carapace. The abdomen is turned downwards and is in constant 

 movement, sweeping out any foreign particles which may have 

 made their way among the feet. Between the abdomen of the 



