732 THE DESCENT OF MAK 



the wind-up, it rises again into a very quick trill on C sharp 

 andD." 



A critic has asked how the ears of man, and he ought 

 to have added of other animals, could have been adapted 

 by selection so as to distinguish musical notes. But this 

 question shows some confusion on the subject; a noise is 

 the sensation resulting from the coexistence of several aerial 

 "simple vibrations" of various periods, each of which inter- 

 mits so frequently that its separate existence cannot be per- 

 ceived. It is only in the want of continuity of such vibra- 

 tions, and in their want of harmony inter se, that a noise 

 differs from a musical note. Thus an ear to be capable of 

 discriminating noises — and the high importance of this power 

 to all animals is admitted by every one — must be sensitive 

 to musical notes. We have evidence of this capacity even 

 low down in the animal scale; thus Crustaceans are pro- 

 vided with auditory hairs of different lengths, which have 

 been seen to vibrate when the proper musical notes are 

 struck." As stated in a previous chapter, similar observa- 

 tions have been made on the hairs of the antennae of gnats. 

 It has been positively asserted by good observers that spi- 

 ders are attracted by music. It is also well known that 

 some dogs howl when hearing particular tones." Seals ap- 

 parently appreciate music, and their fondness for it "was 

 well known to the ancients, and is often taken advantage 

 of by the hunters of the present day." " 



Therefore, as far as the mere perception of musical notes 

 is concerned, there seems no special difficulty in the case of 

 man or of any other animal. Helmholtz has explained, on 

 physiological principles, why concords are agreeable and 

 discords disagreeable to the human ear; but we are little 



8» Helmholtz, "TMorie Phys. de la Musique," 1868, p. 187. 



'' Several accounts have been published to this effect. Mr. Peach writes 

 to me that he has repeatedly found that an old dog of his howls when B flat 

 is sounded on the flute, and to no other note. I may add another instance of a 

 dog always whining, when one note on a concertina, which was out of tune, 

 was played. 



»* Mr. R. Brown, in "Proo. Zoolog. Soc," 1868, p. 410. 



