Origin of Different Kinds of Adaptations 373 



organs in one sex appear in the light of adaptations to certain 

 instincts in the other sex. It would, perhaps, appear to 

 simplify the problem to deny outright that any such relation 

 exists ; but I think, in the light of the evidence that we have, 

 this procedure would be like that of the proverbial ostrich, 

 which is supposed to stick its head in the sand in order to 

 escape an anticipated danger. If we assumed this agnostic 

 position, we might attempt to account for the appearance of 

 secondary sexual organs as mutations that had appeared in 

 one sex, and had no immediate connection with the other 

 sex ; and, so long as these organs were not directly and 

 seriously injurious, we might assume that the animals in 

 which such structures had appeared might be able to exist. 

 But, on the other hand, I think that an examination of the 

 evidence will show that this way out of the difficulty is not 

 very satisfactory, for the organs in question appear, in some 

 cases at least, to be closely connected with certain definite 

 responses in the other sex. Moreover, as Darwin has so 

 insistently pointed out, the action of the males is of such a 

 sort that it is evidently associated with the presence of the 

 secondary sexual organs which they often display before the 

 other sex. Furthermore, the greater and often exclusive 

 development of these organs during the sexual period dis- 

 tinctly points to them as in some way connected with the 

 relation of the sexes to each other. And finally, there is a 

 small, although not entirely convincing, body of evidence, 

 indicating that the female is influenced by the action of 

 the male ; but I do not think that this evidence shows 

 that she selects one individual at the expense of all 

 other rivals.- We meet here with a problem that is as pro- 

 foundly interesting as it is obscure. In fact, if we admit 

 that this relation exists we have a double set of conditions to 

 deal with : first, the development in the males of certain 

 secondary sexual organs ; and secondly, the instinct to dis- 

 play these organs. The supposed influence of the display on 



