316 SEXUAL SELECTION: MAtf. [Fart II. 



incessantly used during the breeding-season, and which 

 are often more highly developed in the male than in the 

 female. The male alone of the tortoise utters a noise, and 

 this only during the season of love. Male alligators roar 

 or bellow during the same season. Every one knows how 

 largely birds use their vocal organs as a means of court- 

 ship ; and some species likewise perform what may be 

 called instrumental music. 



In the class of Mammals, with which we are here more 

 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 absolutely mute 

 excepting at this season. Both sexes of other species, or 

 the females alone, use their voices as a love-call. Con- 

 sidering 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 considering 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 any good evi- 

 dence that these organs are used by male mammals to 

 charm the females. The American Mycetes car ay a per- 

 haps forms an exception, as does more probably one of 

 those apes which come nearer to man, namely, the Ilylo- 

 bates agilis. This gibbon has an extremely loud but mu- 

 sical voice. Mr. Waterhouse states, 28 " 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 I do not doubt 

 that a good "violinist would be able to give a correct idea 



28 Given in W. C. L. Martin's ' General Introduct. to Nat. Hist, oi 

 Maram. Animals,' 1841, p. 432 ; Owen, 'Anatomy of Vertebrates,' vol. iii, 

 p. 600. 



