SEXUAL SELEOTIOIr 485 



Bates found that it is connected "with an nnasual develop- 

 ment of the trachea and vocal organs." It is dilated when 

 the bird utters its singularly deep, loud, and long-sustained 

 fluty note. The head-crest and neck-appendage are rudi- 

 mentary in the female." 



The vocal organs of various web-footed and wading- 

 birds are extraordinarily complex, and differ to a certain 

 extent in the two sexes. In some cases the trachea is 

 convoluted, like a French horn, and is deeply imbedded 

 in the sternum. In the wild swan {Gygnus ferus) it is 

 more deeply imbedded in the adult male than in the adult 

 female or young male. In the male Merganser the en- 

 larged portion of the trachea is furnished with an addi- 

 tional pair of muscles." In one of the ducks, however, 

 namely Anas punctata, the bony enlargement is only a 

 little more developed in the male than in the female." 

 But the meaning of these differences in the trachea of the 

 two sexes of the Anatidse is not understood; for the male 

 is not always the more vociferous; thus with the common 

 duck, the male hisses, while the female utters a loud 

 quack."' In both sexes of one of the cranes {^Orus virgd) 

 the trachea penetrates the sternum, but presents "certain 

 sexual modifications." In the male of the black stork 

 there is also a well-marked sexual difference in the length 

 and curvature of the bronchi." Highly important struc- 

 tures have, therefore, in these cases been modified ac- 

 cording to sex. 



It is often difficult to conjecture whether the many 



« Bates, "The Naturalist on the Amazons," 1863, vol. ii. p. 284; Wallace, 

 in "Proc. Zool. Soc," 1850, p. 206. A new species, with a stiU larger neck- 

 appendage (C. penchdiger), has lately been discovered, see "Ibis," vol. i. p. 457. 



■^ Bishop, in "Todd's Cyclop, of Anat. and Phys.," vol. iv. p. 1499. 



« Prof. Newton, "Proc. Zoolog. Soc," 1871, p. 651. 



•" The spoonbill (Platalea) has its trachea convoluted into a figure of eight, 

 and yet this bird (Jerdon, "Birds of India," vol. iii. p. 763) is mute; but Mr. 

 Blyth informs me that the convolutions are not constantly present, so that per- 

 haps they are now tending toward abortion. 



« "Elements of Comp. Anat.," by R. Wagner, Eng. translat., 1845, p. 111. 

 With respect to the swan, as given above, TarreU's "Hist, of British Birds," 

 M edit., 1845, voL Ui. p. 193. 



