CHAPTER VIII. 



THE EYIDEi^CE FKOM SECONDARY SEXUAL CHAEACTERS. 



The Nature of this Sort of Evidence, 



I HAVE already given many reasons for believing that 

 the male reproductive organ is es2')ecially adapted for 

 gathering up the gemmules which are thrown off by the 

 cells of the body; and for transmitting them to the 

 next generation by impregnation, thus giving rise to 

 variation; while the transmission of the gemmules which 

 are formed in the body of the female is not thus pro- 

 vided for. 



If this supposition is correct, we should expect to find 

 that a variation which first appears in a male should 

 have more tendency to become hereditary than one 

 which first appears in a female. Any slight change in 

 either the male or the female body will, as we have al- 

 ready seen, cause all the cells which are either directly 

 or indirectly influenced by the change to throw off gem- 

 mules. This will happen in a female body as well as in 

 a male body, but the gemmules are, in the latter case, 

 ^ much more likely to be transmitted to descendants, and 

 thus to give rise to more extended modification. 



We should also expect to find that an organ which is 

 confined to males is much more likely tlian one which is 

 confined to females to undergo hereditary changes, for 

 even if the parts of the female body give rise to gem- 

 mules as frequently as the parts of the male body, the 

 chance of transmission is much less. 



We should also expect to find that parts which are 



