36S 



ARTHROPODA 



is not so well developed, and in some cases is represented l>y two 

 bunches of bristles. 



ao 



Fig. 3S4. — Ei\]Jiie (orie!.\ showing the brood jiiuch lillcd with eggs ami young. 

 a'-, second antenna; no, adhesive organ; b, brain;/, furca; li, heart; /, intestine; /, liver; 

 5, shell gland. 



Fig. 3S5. — Piflplotniis caslor. l\ ventral nerve cord; ,!,'. brain with naupluis eve; //, 

 heart, beneath it the ovary and digestive tract; sf). spermalophores; 1, j, lirst and 

 second antenn;u; 3, mandibles; 4, inaxilUc; 5, ntaxillipei-1; O-io, swinmting feet. 



The first pair of antenna? in the males may be hooked near llic base for 

 clasping; the second are sometimes biramous (fig. 374, //). The mandible 

 (fig. 374, ///, r) is instructive, since a study of several species shows that it is 

 derived from a schi;iopodal condition and that the first basal joint alone is used 

 for chewing, the rest being reduced to a palpus of varving development. Both 



