568 The Descent of Man. Part III. 



Unfortunately, its habits have never been closely observed in a 

 Btate of nature ; but from the analogy of other animals, it is 

 probable that it uses its musical powers more especially during 

 the season of courtship. 



This gibbon is not the only species in the genus which sings, 

 for my son, Francis Darwin, attentively listened in the Zoo- 

 logical Gardens to H. leuciscus whilst singing a cadence of three 

 notes, in true musical intervals and with a clear musical tone. 

 It is a more surprising fact that certain rodents utter musical 

 sounds. Singing mice have often been mentioned and exhibited, 

 but imposture has commonly been suspected. We have, how- 

 ever, at last a clear account by a w T ell- known observer, the Eev. 

 S. Lockwood, 31 of the musical powers of an American species, 

 the Hesperomys cognatus, belonging to a genus distinct from that 

 of the English mouse. This little animal w 7 as kept in confine- 

 ment, and the performance was repeatedly heard. In one of the 

 two chief songs, " the last bar would frequently be prolonged to 

 " two or three ; and she would sometimes change from C sharp 

 " and D, to C natural and D, then warble on these two notes 

 " awhile, and wind up with a quick chirp on C sharp and D. 

 " The distinctness between the semitones was very marked, and 

 " easily appreciable to a good ear." Mr. Lockwood gives both 

 songs in musical notation; and adds that though this little 

 mouse " had no ear for time, yet she would keep to the key of B 

 " (two flats) and strictly in a major key." ..." Her soft clear 

 " voice falls an octave with all the precision possible ; then at the 

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

 " and D." 



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 shews some 

 confusion on the subject ; a noise is the sensation resulting from 

 the co-existence of several aerial "simple vibrations" of various 

 periods, each of which intermits so frequently that its separate 

 existence cannot be perceived. It is only in the want of con- 

 tinuity of such vibrations, 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 sen- 

 sitive to musical notes. We have evidence of this capacity even 

 low down in the animal scale : thus Crustaceans are provided 

 with auditory hairs of differeni; lengths, w^hich have been seen to 

 vibrate when the proper musical notes are struck. 32 As stated 



31 The 'American Naturalist,' 32 Helmholtz, 'Thebrie Phys. df 



1871, p. 761. 'a Musique,' 1808, p. 187. 



