THEORY OF SEX-DIMORPHISM 93 



the problem of the origin of the sex-characters 

 is not different from that of the origin of any 

 of the species-characters. We have, indeed, 

 to assume that in the course of time the 

 species-character varied in rather a novel way, 

 but it seems to have been a common thing 

 in the course of evolution that an apparently 

 new organ should arise by a transformation 

 of a very old structure. Thus the spinnerets 

 of a spider are very novel contrivances, but 

 they represent transformed abdominal limbs ; 

 the serpent's fangs are folded or channelled 

 teeth, and its reservoirs of venom are special- 

 ised glands of the mouth and lips ; a bird's 

 feather is part of a reptile's scale glorified; 

 and the hammer and anvil that form part of 

 the delicate apparatus for conveying vibrations 

 from the drum to the inner ear were once part 

 and parcel of the rougher and more common- 

 place mechanism of the jaws. There is abun- 

 dant analogy, then, in support of the view 

 that ordinary species-characters may be trans- 

 formed into sex-characters. But the origin 

 of the transformation remains obscure. More- 

 over, there are many sex-characters which 

 cannot be traced back to specific characters 

 common to the two sexes. Finally, care must 

 be taken not to invest the internal secretions 

 with more than a trigger-pulling and quanti- 

 tative influence. 



Having cleared the ground, we come back 

 to the vague proposition that sex -characters 

 arise as germinal variations. Here, it may 

 be, we are up against a fundamental character 

 of organisms, that they continually tend to 

 vary and often to vary creatively. But let 



