34 THOUGHTS UPON THE MUSICAL SENSE [X. 



In this way is explained the evolution of every useful qualit}^ 

 and the adaptation which is so manifest in all living beings. 



It is, however, very probable that the animal world is also 

 subject to a selective process of another kind,— the sexual 

 selection of Charles Darwin. I will devote a few words to 

 this principle, inasmuch as our main subject is immediately 

 connected with it. 



We are all familiar with the song of the grasshopper and 

 cricket. If one walks in the meadows along a little brook on 

 a fine June evening, he will often hear a long-sustained note, 

 even, subdued, and pleasant, which vibrates powerfully without 

 swelling or diminishing, somewhat like that of the nightingale 

 in Haydn's 'Toy Symphony.' A cautious approach will 

 enable us to see a mole-cricket sitting, apparently motion- 

 less, in front of its hole in the ground. More careful examina- 

 tion proves that the short wing-covers are in a state of continual 

 vibration, producing friction as they move ; and this it is which 

 causes the sound. The microscope shows that minute and 

 dehcate teeth are placed at regular intervals along a vein on 

 one of the wing-covers ; when these are struck at a certain 

 rate by a vein on the other wing, they emit a whirring note of 

 a definite pitch. One vein acts as the bow, the other as the 

 string of a vioUn ; the mole-cricket is a viohnist, and can there- 

 fore hold on its note as long as it will. 



It is evident that the power of producing a song can be of no 

 value to these animals in the struggle for existence. It neither 

 helps them to find food, nor defends them from their enemies : 

 it is therefore impossible that it can have arisen by the opera- 

 tion of natural selection. Furthermore, when we enquire into 

 its mode of origin we must take into account the fact that only 

 the males possess the gift of song. This is also true of all 

 other singing insects, such for instance as grasshoppers. The 

 ancient Greeks were aware of this, for Xenarchus, in one of his 

 comedies, says, ' Are not the cicadas happy, whose wives have 

 not got an atom of voice ^' 



Here then we find the solution of the problem ; the origin of 

 the sound-producing apparatus receives a simple explanation 

 in the contest between the males for the possession of the 

 females. If we take it for granted that the females are pleased 



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