24:0 THE PLAY OF ANIMALS. 



means of recognition between the two sexes of a species, 

 and as an invitation from the male to the female bird." 

 These acoustic signals become very important when the 

 members of a species live far apart, and are of especial 

 service to migratory birds whose males first arrive 

 at the destination and call to their mates to follow. 

 The male that is distinguished for the " clearness, loud- 

 ness, and individuality '' of his song would succeed first 

 in accomplishing this, and has thus an advantage that 

 may be decisive in the struggle for life. But in that 

 case the clearness, loudness, and individuality of his 

 song would be a sufficient object for the operation of 

 natural selection.* A close examination of these cita- 

 tions shows, I think, that while they modify the Dar- 

 winian theory very considerably, they do not exclude it. 

 It would, indeed, be absurd to affirm that all bird- 

 songs originate in a conscious esthetic and critical act 

 of judgment on the part of the female. A conscious 

 choice either of the most beautiful or the loudest singer 

 is certainly not the rule, and probably never occurs at 

 all. But is it not still a choice, though unconscious, 

 when the female turns to the singer whose voice, 

 whether from strength or modulation, proves most at- 

 tractive? Even if the song is primarily a means of 

 recognition or an invitation from the male, still the 

 psychological effect must be that the female follows the 

 songster that excites her most, and so exerts a kind of 

 unconscious selection. 



But this is essentially the Darwinian idea, since, 

 though there is indeed no conscious aesthetic selection, 



* On this point I a^ree with E. von Hartmann's penetrating 

 criticism of the Darwinian theory. See especially his Philosophie 

 des Unbewussten, iii, p. 435. 



