2Q2 S. J. HOLMES. 



ford many cases in which the association of the two sexes is 

 prolonged for a considerable period. The males of Artcmia 

 clasp the females with their peculiarly modified antennae and the 

 two sexes swim about together for several days (Leydig). 

 Among the free-swimming copepods the male may continue 

 clasping the female for some hours after, as well as before, de- 

 positing the spermatophore (Jurine, von Siebold). And among 

 the Cumacea Dohrn has observed the males swimming about 

 upon the backs of the females, much as in Amphipoda. The 

 tendency for the association of the sexes greatly to exceed the 

 act of copulation is apparently quite widespread among the 

 Crustacea ; and although, so far as is known, the mating instinct 

 of the Gammaridea is much the same throughout the group so 

 that we cannot trace the successive steps in its development, the 

 sexual behavior of some of the lower Crustacea presents many 

 features which may serve to throw some light upon its origin. 



