season I have not observed, but it certainly happens out of the pairing season. I have several times heard blackbirds singing alternately in June. But the most conspicuous instance is supplied by the redbreasts. These habitually sing against one another during the autumn months: reply and rejoinder being commonly continued for five minutes at a time.
Even did the evidence support the popular view adopted by Mr. Darwin, that the singing of birds is a kind of courtship—even were there good proof, instead of much disproof, that a bird's song is a developed form of the sexual sounds made by the male to charm the female; the conclusion would, I think, do little toward justifying the belief that human music has had a kindred origin. For, in the first place, the bird-type in general, developed as it is out of the reptilian type, is very remotely related to that type of the Vertebrata which ascends to Man as its highest exemplar; and, in the second place, song-birds belong, with but few exceptions, to the single order of Insessores—one order only, of the many orders constituting the class. So that, if the Vertebrata at large be represented by a tree, of which Man is the topmost twig, then it is at a considerable distance down the trunk that there diverges the branch from which the bird-type is derived; and the group of singing-birds forms but a terminal subdivision of this branch—lies far out of the ascending line which ends in Man. To give appreciable support to Mr. Darwin's view, we ought to find vocal manifestations of the amatory feeling becoming more pronounced as we ascend along that particular line of inferior Vertebrata out of which Man has arisen. Just as we find other traits which pre-figure human traits (instance arms and hands adapted for grasping) becoming more marked as we approach Man; so should we find, becoming more marked, this sexual use of the voice, which is supposed to end in human song. But we do not find this. The South American monkeys ("The Howlers," as they are sometimes called), which, in chorus, make the woods resound for hours together with their "dreadful concert," appear, according to Rengger, to be prompted by no other desire than that of making a noise. Mr. Darwin admits, too, that this is generally the case with the gibbons: the only exception he is inclined to make being in the case of Hylobates agilis, which, on the testimony of Mr. Waterhouse, he says ascends and descends the scale by half-tones. This comparatively musical set of sounds, he thinks, may be used
- It is far more probable that the ascents and descents made by this gibbon consisted of indefinitely-slurred tones. To suppose that each was a series of definite semi-tones strains belief to breaking point; considering that among human beings the great majority, even of those who have good ears, are unable to go up or down the chromatic scale without being taught to do so. The achievement is one requiring considerable practice; and that such an achievement should be spontaneous on the part of a monkey is incredible.