No. 632] SECONDARY SEXUAL CHARACTERS 225 



more like those of the female (Fig. 1 C). The other in- 

 dividuals had abdomens not quite so broad as those of 

 typical females of the same size, Fig. 4 B\ yet their 

 claws were generally small, like those of the female, and 

 showed no indications of a variation towards the male 

 type. Since the younger stages of some crabs, such as 

 the blue crab, have a narrower abdomen than that of the 

 adult female until the last molt, it seemed possible that 

 these "intersexes" might at a later molt turn into typi- 

 cal females. They were kept therefore and well fed for 

 two or three months during which time they molted once, 

 Fig. 4 B" , or even twice. A comparison of the old skin 

 showed that the condition of the abdomen and claws had 

 not changed. It is evident that this condition can not be 

 explained as transitory. Nor is it juvenile because nor- 

 mal individuals of the same size have the abdomen full 

 width. 



A more detailed examination of these two types may 

 now be given. The most striking fact is that all of 

 the full grown crabs belong to one category, and all of 

 the smaller ones to another. The former of which there 

 are six, have a strictly male abdomen regardless of the 

 condition of their claws, and what is more significant the 

 external genital pores are at the base of the last pair of 

 legs, as in the normal male. As shown in Fig. 2 A' and 

 B', the abdomen is exactly like that of the male. On its 

 inner side it contains the two long copulatory appendages 

 of the male. The chelss in three individuals are small, 

 Fig. 4 B, and of the same size, resembling those of the 

 female. In the other three one of the claws is somewhat 

 larger, Fig. 4 A, than the other and shows unmistakably 

 evidence of variation toward the male. The genital pores 

 are, as stated, in the same position as in the normal male, 

 and there are no indications of female pores further 

 forward. In two cases at least, the crabs molted, but did 

 not change their characters. In the second group, Figs. 

 A, B, C, D, there are sixteen individuals. There is 

 amongst these no obvious relation between the size of the 



