SEXUAL SELECTION 



09t 



tinguishing character does not refer merely to finding the female, but 

 to holding her fast, or, as we may say, to capturing her. 



Thus the males of the Copepods possess on their anterior 

 antennae an arrangement which enables them to throw a long whip- 

 like structure like a lasso round the head of the female as she rapidly 

 swims away. The antenna? of the male Daphnids, too, are in one 

 genus (Moina) developed into a grasping apparatus, instead of into 

 smelling organs as in Leptodora. Fig. 57 shows the male. Fig. 58 the 

 female oi Moina paTadoxa\ the first antenn^^ of the male are not 

 only much longer and stronger than those of the female {at^), but 

 they are also armed with claws at the end, so that the males can catch 



schr sch 



Fig. 57. Moina paradoxa, male. at^. first antennae, with claws at the tip for 

 capturing the female, at'-, second antennse. fkr, claws on the first pair of legs 

 for clambering, gh, brain. Ibi; upper lip. vicl, mandible, md, mid-gut, with the 

 liver lobes (Wt). /«, heart, sp, testis. o/Y, anus. s6, caudal setae. sAr, caudal claws. 

 sch, shell, schr, cavity of the shell, kie, gill-i^lates. Magnified 100 times. 



their mates as with a fork, and hold them fast. And even that was 

 not enough, for, in addition, the males of most Daphnids possess 

 a large sickle-shaped but blunt claw on the first pair of legs (Fig. 

 57, fl^r), which enables them to cling to the smooth shell of the 

 female, and to clamber up on it to get into the proper position for 

 copulation. 



If we in(juire into the manner of the origin of secondary sexual 

 characters of this kind, we shall find that both may have been in- 

 creased by sexual selection, for a male with a better sickle will succeed 

 more quickly in getting into the proper position for copulation than 

 one with a less perfect mechanism. This assumption does not rest 

 I. ' p 



