SEXUAL SELECTION 681 



enlargement of bis Tooal organs would be intelligible on 

 the principle of sexual selection, together with inheritance 

 limited to the same sex and season; but we have no evi- 

 dence in favo" of 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 court- 

 ship or battles, or in any other way. But may we not be- 

 lieve that the frequent use of the voice, under the strong 

 excitement of love, jealousy, and rage, contiuued during 

 many generations, may at last have produced an inherited 

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

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

 of knowledge, the most probable view. 



The voice of the adult male gorilla is tremendous, and 

 he is furnished with a laryngeal sac, as is the adult male 

 orang.* The gibbons rank among the noisiest of monkeys, 

 and the Sumatra species (^Hylobates syndactylus) is also fur- 

 nished with an air-sac; but Mr. Blyth, who has had oppor- 

 tunities for observation, does not believe that the male is 

 noisier than the female. Hence, these latter monkeys prob- 

 ably use their voices as a mutual call, and this is certainly 

 the case with some quadrupeds; for instance, the beaver.* 

 Another gibbon, the H. agilis, is remarkable from having 

 the power of giving a complete and correct octave of musi- 

 cal notes,* which we may reasonably suspect serves as a sex- 

 ual charm ; but I shall have to recur to this subject in the 

 next chapter. The vocal organs of the American Mycetes 

 caraya 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 

 vrith their overwhelming voices. The males begin the dread- 

 ful concert, aUd often continue it during many hours, the 



* Owen, "Anatomy of Vertebrates," voL iii. p. 600. 



" Mr. Green, in the "Journal of the linnaean Society," vd. x. Zoology, 

 1869, p. 362. 



» C. L. Martin, "(Jeneral Introduction to the Nat. Hist, of Mamm. Ani- 

 mals," 1841, p. 431, 



