356 THE HUMAN SPECIES 



her power. The regularity, rapidity and certainty with which 

 the animal screams out the scale is extremely remarkable. 

 The ape herself appears to be very much excited by it, as 

 every muscle is thrown into contraction, and her whole body 

 is shaken by a shivering movement." This is in effect a true 

 song, although it only consists in repeating the same scale over 

 and over again. The song of the singing house mouse is 

 quite different, and is often mistaken by the uninitiated for 

 the squeaking of young mice in their nest. But it is really 

 no mere squeaking noise, but a perfect song moving in accurate 

 intervals, and produced by a full-grown mouse, as I was able 

 to observe long ago in a singing mouse which I kept in 

 captivity. Bamfield has explained the song of the house 

 mouse in his home as an imitation of that of a canary in his 

 kitchen, which is not so very improbable considering the well- 

 known fondness of house mice for music. Other observers, 

 however, besides myself, have noted that the house mouse 

 will sing quite independently of hearing a canary. The only 

 remarkable thing is that singing mice are so seldom heard, as 

 it has been proved that they form no special class of mice, 

 but are only of the ordinary variety found in houses. 



These two examples of singing mammals have no real con- 

 nection with singing birds, and these differ from one another 

 though comprised in allied orders. Their distinguishing mark 

 is the possession of five or six pairs of muscles in the larynx 

 which produce the characteristic sounds. At the same time all 

 birds possessing this apparatus cannot be accurately classed as 

 singing birds ; ravens and birds of paradise can only produce 

 a kind of shriek. The remaining birds are more definitely 

 song birds, finches, yello\v-hammers, tanagers, stilts, pipers, 

 tomtits, tailor birds, thrushes, starlings and butcher birds. 

 The very various songs of the birds may be classed in three 

 groups according to their loudness, their beauty of tone and 

 their richness. Those birds are said to warble whose voice 

 is strong and sweet, and whose song always or generally con- 

 sists of a sequence of notes such as the nightingale, the 

 chaffinch, the canary, the wren and the black-cap ; those birds 

 are simply said to sing when their notes flow forth without 

 any regular sequence, mingled with softer twittering sounds, 



