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SEXUAL SELECTION: max 
Part II- 
move particularly concerned, the males of almost all the 
species use their voices during the breeding-season 
much more than at any other time ; and some are abso- 
lately mute excepting at this season. Both sexes of other 
species, or the females alone, use their voices as a love- 
call. Considering these facts, and that the vocal organs 
of some quadrupeds are much more largely developed 
in the male than in the female, either permanently or 
temporarily during the breeding season ; and consider- 
ing that in most of the lower classes the sounds produced 
by the males, serve not only to call but to excite or allure 
the female, it is a surprising fact that we have not as yet 
an y good evidence that these organs are used by male 
mammals to charm the females. The American Sfycstss 
caraya perhaps forms an exception, as does more pro- 
bably one ot those apes which come nearer to man, 
namely, the Hylobates agilis. This gibbon has an 
extremely loud but musical voice. Mr. Waterhouse 
states," “It appeared to me that in ascending and 
‘ descending the scale, the intervals were always exactly 
"half-tones; and I am sure that the highest note was 
the exact octave to the lowest. The quality of the 
^ notes is very musical ; and 1 do not doubt that a good 
“ Uolinist would be able to give a correct idea of the 
gibbons composition, excepting as regards its loud- 
“ ness - ’ Mr. Waterhouse then gives the notes. Pi' 0 ' 
lessor Owen, who is likewise a musician, confirms the 
foregoing statement, and remarks that this gibbon 
“alone of brute mammals may be said to sing.” U 
appears to be much excited after its performance. Un- 
fortunately its habits have never been closely observed 
in a state of nature ; but from the analogy of almost 
28 Given in W. G. L. Martin’s ‘General Introduet. to Nat. Hist, of 
Mamm. Animals, 1841, p. 432; Owen, ‘Anatomy of Vertebrates,’ v0 * 
iii. p. 600. 
