ORIGIN OF SONG 161 



words, the song is always specific, and this is 

 the most noticeable, as it is the most remarkable, 

 characteristic. 



There is still, however, another quality to 

 which I would draw attention — that of loud- 

 ness. The sounds produced are on the 

 whole alike penetrative, and the individuals 

 of any given district, even though the cli- 

 mate by aflfecting their vocal muscles may 

 have modified the character of the song, are 

 at no disadvantage in this respect ; neither are 

 the females on the same account the less likely 

 to hear the undeveloped voice of the immature 

 male. 



We have then the following considerations : 

 firstly, there is the widespread and remarkable 

 phenomenon of imitation, from which we can 

 infer that the diversity of song is not due to 

 structural differences but must be sought in 

 some innate capacity to play one tune in 

 preference to another ; secondly, not all the 

 individuals of the same species play a similar 

 tune — we find that there is in certain directions 

 a noticeable variation which nevertheless does 

 not seem to affect the question of success or 

 failure in the attainment of reproduction ; in 

 the third place, in contrast with this variation, 

 we can observe a striking uniformity in two 

 important particulars, namely in the specific 

 character and penetrative power of the song — 

 qualities which we know are essential for the 

 purposes of " recognition " and " warning " ; and 

 finally, from the general course of our investi- 



