PHYLUM ARTHROPODA 



".71 



Artemia (the Brine-sbrimp) (Jnosiracn) 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 iinjointed 

 stalks. In Limnotis (2), on the other hand, and in Estheria (.3) 

 the carapace takes the form of a shell, formed of two parts 

 or valixa, united in Estheria by a hinge, and resembling the 

 shell of a cockle or other bi\alved mollusc. The limbs have the 

 same general structure as those of Apus, but the antennae are 







l.Branchipus 



ant. 2 



3 . E s !• h e r i a 



Fir.. 448. — Three Branchiopoda. Tn 3, « is the .shell ; h the animal with one valve of the shell 

 removed, itvt'^. antennnle ; fivf\ .antenna ; hf. heart ; rii. adductor muscle ; md, mandible ; 

 or. ovar}' ; a. unpaired process from head ; j). copulatory appendages ; sh.gl. shell-gland ; 

 t. testis. (After Gerstaecker.) 



often of considerable size, and are sometimes modified into 

 prehensile organs. 



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

 (Fig. 449, 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 verj;- 

 imperfect, and the whole body, but not the head, 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 female and the posterior part of the carapace 

 is a large hrood-poiich (hr.p), in which the eggs are stored. Tho 



