498 



LIFE : OUTLINES OF GENERAL BIOLOGY 



tures with complicated musculature and skeleton. In the Chimaera 

 they are even more complicated. They are very definitely male 

 organs, and in some cases at least they arc inserted into the cloaca 

 of the female in the process of sexual union. Phyletically they are 

 specialised portions of the pelvic fins, but there is no trace of them 

 in the female. So far as we know, there is no warrant for supposing 

 that the ancestors of "ir modern Selachians had in both sexes 

 structures like the claspers. 



Similarly, the male spider is often very markedly distinguished 

 from the female not only in size, but by the great complexity of the 



Fig. 72. 



Se.\ Dimorphism in Spiders. Minute male (M) and much larger female (F). 



After Vinson. 



jx^dipalps which arc used in transferring the sperms into the female. 

 The se.v-charactcr here is not the pedipalp, which is, of course, com- 

 mon to both sexes, but the extraordinary elaboration of the end of 

 tliis appendage. W'c do not know of any warrant for regarding this 

 as other than a purely masculine character. 



Again, in most Mammals the testes are carried in an external 

 pouch or scrotum (into which they descend, as if by a normahsed 

 rupture, at a certain stage of development), while the ovaries always 

 remain internal. This is a definite male pecuHarity, an extra thing 

 that is not hinted at in the female: and we do not know of any 

 warrant for regarding this as a transformation of a specific character 

 once common to the two sexes. In the same way the protruding 



