{ hi ap. XV I II. Mammals- — Vocal Organs. 527 



imitate her cry. If we could believe that the male had the 

 power to excite or allure the female by his voice, the periodical 

 enlargement of his vocal organs would be intelligible on the 

 principle of sexual selection, together with inheritance limited to 

 the same sex and season ; but we have no evidence in favour ot 

 this view. As the case stands, the loud voice of the stag during 

 the breeding-season does not seem to be of any special service to 

 him, either during his courtship or battles, or in any other way. 

 But may we not believe that the frequent use of the voice, xmd.e! 

 the strong excitement of love, jealousy, and rage, continued 

 during many generations, may at last have produced an in- 

 herited effect on the vocal organs of the stag, as well as of other 

 male animals? This appears to me, in our present state ot 

 knowledge, the most probable view. 



The voice of the adult male gorilla is tremendous, and he is 

 furnished with a laryngeal sack, as is the adult male orang^ 

 The gibbons rank among the noisiest of monkeys, and the 

 Sumatra species (Bylobates syndactylus) is also furnished with an 

 air sack ; but Mr. Blyth, who has had opportunities for observa- 

 tion, does not believe that the male is noisier than the female. 

 Hence, these latter monkeys probably use their voices as a 

 mutual call ; and this is certainly the case with some quadrupeds, 

 for instance the beaver. 5 Another gibbon, the B. agilis, is re- 

 markable, from having the power of giving a complete and 

 correct octave of musical notes, which we may reasonably sus- 

 pect serves as a sexual charm ; but I shall have to recur to this 

 subject in the next chapter. The vocal organs of the American 

 Mycetes caruya are one-third larger in the male than in the 

 female, and are wonderfully powerful. These monkeys in warm 

 weather make the forests resound at morning and evening with 

 their overwhelming voices. The males begin the. dreadful con- 

 cert, and often continue it during many hours, the females, 

 sometimes joining in with their less powerful voices. An 

 excellent observer, Kengger, 7 could not perceive that they were 

 excited to begin by any special cause ; he thinks that, like many 

 birds, they delight in their own music, and try to excel each 

 other. Whether most of the foregoing monkeys have acquired 

 their powerful voices in order to beat their rivals and charm the 

 females — or whether the vocal organs have been strengthened 



talits of the moose and wild rein- 6 C. L. Martin, ' General Intro 



deer. duction to the .Nat. Hist, of Ma mm 



4 Owen, ' Anatomy of Vert©- Animals,' 1841, p. 431. 



brates.' vol. Hi. p. 600, ' ' Naturgetschichte der Sauc-e 



5 Mr. Green, in 'Journal of Linn. thierc von Paraguay,' 1830, s. li 

 Soe.' vol. x. Zoology, 1869, p. 362. 21. 



