310 



FROM NORTH POLE TO EQUATOR. 



more full-toned and sonorous than that of a long-armed ape which 

 I observed in captivity. I was first astonished, then delighted, with 

 these deep notes, uttered with full strength, and by no means dis- 

 agreeable, because perfectly clear and well-rounded. In one species 

 the ringing call, which I should describe as a song rather than a 



Fig. 47. The Hoolock (Hylobates leuciscun), one of the Gibbons. 



cry, begins on the key-note E, ascends and descends in semitones 

 through the chromatic scale for a full octave, sometimes ending 

 with a shrill cry, which seems to be uttered with the animal's whole 

 strength. The key-note remains audible throughout, and serves as 

 a grace-note to each of the succeeding ones, which, in ascending the 

 scale, follow each other more and more slowly, in descending more 

 and more quickly, at last with extreme rapidity, but always with 

 perfect regularity. The notes of some species of the group are said 



