222 THE BIOLOGY OF BIRDS 



claspers of male Selachians and Chimaeroids. In a fish like 

 the skate they are very conspicuous sex-characters ; they are 

 highly specialised structures with complicated musculature 

 and skeleton. In the Chimasra they are even more com- 

 plicated. They are very definitely male organs, and in some 

 cases at least they are inserted into the cloaca of the female 

 in the process of sexual union. Phyletically they are special- 

 ised 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 our modern Selachians had 

 in both sexes structures like the claspers. 



Similarly, the male spider is often very markedly distin- 

 guished from the female not only in size, but by the great 

 complexity of the pedipalps which are used in transferring 

 the sperms into the female. The sex-character here is not 

 the pedipalp, which is of course common to both sexes, but 

 the extraordinary elaboration of the end of this appendage. 

 We do not know of any warrant for regarding this as other 

 than a masculine character. 



Again, in most Mammals the testes are carried in an 

 external pouch or scrotum (into which they descend, as if 

 by a normalised rupture, at a certain stage of development), 

 while the ovaries always remain internal. This is a definite 

 male peculiarity, 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. 



Can Masculine Characters pass to the Female? — In 

 some birds there is an indication of this, and the same 

 is true of many other animals. The point is whether a 

 secondary sex-character, primarily restricted in expression 

 to the male, may find normal occurrence in the female as 

 well — perhaps through some variation in the hormones 

 from the reproductive organs. We know experimentally 

 that the removal of the ovary of a bird may be followed by 

 the development of the masculine plumage, normally 

 inhibited. May not the extension of a mascuHne character 

 to the female have occurred occasionally in natural evolu- 



