The Emdence from Sexual Characters. 179 



nary iion-pamsitic forms; the segmentation of the body 

 is hardly visible, the power of locomotion is entirely 

 lost, and the appendages are either rudimentary or are 

 changed into hooks for clinging to the animal infested 

 by the i^arasite. The male, like the female, has no 

 power of locomotion, and is very much smaller than the 

 female, the difference in size being much greater than 

 tlie two figures would indicate. It is found nowhere 

 except upon the body of the female, to which it clings 

 by its rudimentary feet. The female of another form, 

 Anchorella, is shown in Fig. 15, and the male in Fig. 



Fig. 13. Male specimen of Lernen- Fig. 14. Male specimen of AnchO' 



toma corunta. rella uncinata. 



14. In this species the males are very small as com- 

 pared with the females, to whose bodies they are firmly 

 fastened by their rudimentary hooked limbs. 



We can hardly state with confidence that either sex is 

 more modified than the other in these parasitic cope- 

 pods, for both have undergone such great changes that 

 they have lost all traces of their crustacean aflBnity, but 

 in the very similar case of the barnacles, we have suffi- 

 cient evidence that the males do depart further than 

 the females from the ancestral type. 



The barnacles, or acorn-shells (Fig. 16), are Crustacea 



