MAMMALS-VOCAL ORGANS. 523 



the beaver/ Another gibbon, the H. agilis, is remarkable, from 

 having the power of giving a complete and correct octave of 

 musical notes," which we may reasonably suspect 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 caraya are 

 one-third larger in the maJe than in the female, and are won- 

 derfully powerful. These monkeys in warm weather make the 

 forests resound at morning and evening with their overwhelming 

 voices. The males begin the dreadful concert, and often continue 

 it during many hours, the females, sometimes joining in with 

 their less powerful voices. An excellent observer, Rengger,' could 

 not perceive that they vi^ere 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 and enlarged through the inherited ef- 

 fects of long-continued use without any particular good being thus 

 gained — I will not pretend to say; but the former view, at least 

 in the case of the Hylobates agilis, seems the most probable. 



I may here mention two very curious sexual peculiarities oc- 

 curring in seals, because they have been supposed by some writ- 

 ers to affect the voice. The nose of the male sea-elephant (Ma- 

 crorhinus proboscideus) becomes greatly elongated during the 

 breeding-season, and can then be erected. In this state it is 

 sometimes a foot in length. The female is not thus provided at 

 any period of life. The male makes a wild, hoarse, gurgling 

 noise, which is audible at a great distance and is believed to be 

 strengthened by the proboscis; the voice of the female being 

 different. Lesson compares the erection of the proboscis, with 

 the swelling of the wattles of male gallinaceous birds whilst 

 courting the females. In another allied kind of seal, the bladder- 

 nose (Cystophora cristata), the head is covered by a great hood 

 or bladder. This is supported by the septum of the nose, which 

 is produced far backwards and rises into an internal crest seven 

 inches in height. The hood is clothed with short hair, and is 

 muscular; it can be inflated until it more than equals the whole 

 head in size! The males when rutting, fight furiously on the 

 ice, and their roaring "is said to be sometimes so loud as to 

 "be heard four miles off." When attacked they likewise roar or 

 bellow; and whenever irritated the bladder is inflated and quiv- 

 ers. Some naturalists believe that the voice is thus strengthened, 



° Mr. Green, in 'Journal of Linn. Soc' vol. x. Zoology, 1869, p. 362. 

 C. L. Martin, 'General Introduction to the Nat. Hist, of Mamm, 

 Animals," 1841, p. 431. 

 ' Naturg-eschichte der Saugethiere von Paraguay,' 1830, s. 15, 21. 



