THE CYCLE OF SEX 127 



It is probably unwarrantable to speak of 

 the males getting up their tournaments in 

 order to impress the females. They fight 

 to win the females, they fight because they 

 are jealous, they fight because they are high- 

 strung, they fight because of the irritability 

 induced by unsatisfied sexual appetite, and 

 so on ; but it is very unlikely that they fight 

 " in order " to impress. What probably 

 happens is that certain males in their whole 

 behaviour excite the females more effectively 

 than do others, and are in consequence more 

 successful in reproduction. The type suc- 

 cessful in courtship will naturally tend to 

 define the direction of further evolution. 



Pass now from combat to song, in the old 

 minstrel fashion. Every one recognises that 

 the musical displays of singing birds play an 

 important role in their courtship; and it is 

 well nigh inevitable to draw a similar con- 

 clusion in regard to the instrumental music 

 of crickets, grasshoppers, cicadas, and the 

 like especially in cases where the sound- 

 producing is confined to the males. It is 

 difficult to believe that the noise falls on 

 deaf ears, and yet the evidence is far from 

 conclusive. Instead of collecting represen- 

 tative forms of animal courtship, let us linger 

 over this single question to illustrate the 

 difficulty of the problem. Many insects have 

 sense-organs which may be interpreted as 

 auditory, but there is little direct proof of 

 this. In fact, the numerous experiments 

 that have been made with the hope of definitely 

 settling whether insects hear have not yielded 

 convincing results. They have shown that 



