/. CRUSTACEA: COPEPODA. 



419 



degenerate (figs. 6, 423) as to be recognized even as arthropods 

 only by a knowledge of the development. The sixteen somites of 

 the body are nearly equally divided among the three regions 



i 



FIG. 421. Evadne (orig.), showing the brood pouch filled with eggs and young. a a , 

 second antenna; ao, adhesive organ; b, brain; /, furca; 7i, heart; i, intestine; I, 

 liver; s, shell gland. 



FIG. 422.Dinptomus castor, b, ventral nerve cord; 0, brain with nauplius eye; hr 

 heart, beneath it the ovary and digestive tract; sp, spermatophores ; J, 2, first and 

 second antennae; 3, mandibles; 4, maxillae; 5, maxilliped; 6-10, swimming feet. 



head (6), thorax (5), and abdomen (5) of the animal. (In Cyclops 

 the first thoracic segment is fused with the head, the first two 

 abdominal segments are fused fig. 7.) The terminal abdominal 



