THE RELATIONS OF THE SEXES 169 



after the fashion shown in 111. 23. Confined to the males alone, 

 this lengthening of the tube seems to have been acquired for 

 the sake of increasing the resonance of the voice. 



Though it is undoubtedly remarkable that in two such 

 completely distinct groups the same structural modification 

 should have taken place, we meet with an exact parallel in 

 another fashion of disposing of an elongated windpipe. 



Herein the increased length is disposed of in a series of 

 coils lying between the breast muscles and the skin ! This 

 obtains in certain Passerine birds — related to the Birds of 

 Paradise, many Game-birds, e.g., Curassows, the curious Goose 

 Anseranas, and the Sandpipers known as "Painted Snipes" 

 {Rhynchea). The nature of these coils are shown in Ills. 23. 

 Though we must assume that in all these modifications in- 

 creased resonance of the voice has been secured, either to en- 

 hance the performer in the eyes of its mate during the courting 

 season, or for the more prosaic purpose of indicating the 

 whereabouts of individuals which have got separated, there 

 is but little concrete evidence obtainable at present bearing 

 on the problem. That such elaborate devices should have come 

 about is somewhat puzzling, since many birds continue to make 

 exceedingly powerful and penetrating sounds though possessed 

 of no special sound-producing apparatus whatever. The Ostrich 

 and the Cassowary may serve as striking examples of this, for 

 in both the windpipe and voice organ generally is of a most 

 primitive character. 



We must pass now to a brief review of what we may call 

 instruments of percussion whose purpose is the production of 

 sound. Some of these, however, scarcely come within this 

 category, since the sounds they give forth are due to vibrations 

 set up by their rapid motion through the air. 



The simplest form of percussion music is perhaps that 

 produced by the White Stork. Throwing the head backwards 

 till the point of the beak almost touches the back, the jaws are 

 set rapidly in motion, clashing one against another and produc- 

 ing a curious rattling sound, which has been compared to 

 castanets. As the sound is being produced the head is slowly 

 turned into its normal position ; but not until the beak has 

 described a half-circle and rests almost on the ground does 

 the music cease. This sound, so far as can be made out, 



