Note 324 — Chapter XVI

The song of the gibbon has already been alluded to in a quotation from Darwin. I may here add that the chimpanzee “Sally” not unfrequently executes an extraordinary performance of an analogous kind. The song, however, is by no means so “musical.” It is sung without any regard to notation, in a series of rapidly succeeding howls and screams—very loud, and accompanied by a drumming of the legs upon the ground. She will only thus “break forth into singing” after more or less sustained excitement by her keeper; but more often than not she refuses to be provoked by any amount of endeavour on his part.