84 THE FINCHES 



from any family whatever, much less its own, as some ("horresco referens") 

 have mistakenly attempted to do. For this reason, if for no other 

 for who would not redress an injury when it lies in his power to do so ? 

 I place Loxia curvirostra first upon my list. 



The use, and consequent raison d'etre of the above-mentioned 

 strange abnormality has now long been thought a part of our know- 

 ledge. Yet it is perhaps not quite certain that the mere outward shape 

 of the mandibles unique though it be has anything to do with the 

 bird's feeding habits. For what are the facts ? As first explained by 

 Townson, and afterwards, more scientifically, by Yarrell, the mechanism 

 of the required bones and muscles is such that, on the mandibles being 

 opened sufficiently widely but no more for the tips to meet, these, 

 though crossed before, do now so meet, becoming opposed to each 

 other, in a straight line. The bill, therefore, instead of being a double- 

 pointed instrument, as it was just before, is changed, for the nonce, 

 into one of the more ordinary type, only broader, and is thus inserted 

 between the scales, preferably, of a fir-cone, when, being opened still 

 wider, the mandibles now again diverge laterally, but to a much greater 

 degree, and with such power that the scales are forced wider apart, 

 and, the seeds lying between them being thereby loosened, the bird 

 extracts them with its tongue, which, to complete the perfection of the 

 adaptation, acts after the manner of a scoop. 



But what part, it may be asked, is played in all this by the cross- 

 ing of the bird's bill, in the manner peculiar to it, when closed ? 

 Were it of the usual shape it could still be inserted perhaps with 

 equal efficacy between the scales, and its subsequent lateral exten- 

 sion in the way described should then, as now, do the rest. If so, 

 then that peculiar conformation which so strikes the eye, and gives 

 its name to the species, is but incidental to the general scheme of the 

 mechanism, 1 in which case the crossbill, as such, must be looked upon 

 not as a main proposition in evolutionary physiology, but as a corollary 



1 It may even have become a secondary sexual character, since it would appear that the 

 cross is more pronounced in the male than the female, and is also subject to much variation. 

 See British Birds, January 1910. 



