2o6 Variations and Orthoplasy 



Of course the availability of this case as an illustration 

 of organic selection — apart from the facts — would de- 

 pend upon whether the flexible attachment of the upper 

 mandible did supplement the curvature of the bill, or take 

 the place of it, in the early stages of the adaptation. This 

 appears the more likely from the further fact that this 

 same character, the relatively loose attachment and some- 

 what free muscular play of the upper mandible, is useful 

 for other purposes as well. In feeding, the parrot makes 

 much use of these muscles, using his mandibles as a 

 nut-cracker, and in general for crushing hard objects 

 between them. It also comes in 'handy,' so to speak, 

 in a variety of those gymnastic feats whereby he exer- 

 cises his agility in a manner truly serpentine, using his 

 beak as a claw for holding on and lifting himself. In all 

 this the flexibihty of the upper mandible is of direct 

 advantage.^ It is also well known that the vibration 

 of the upper mandible greatly enriches the range and 

 variety of bird song, and in this case it may be of 

 great utility in the parrot's extraordinary power of articu- 

 lation. 



If this be a true construction of the facts of the case, it 

 will at once be seen to illustrate the correlation of varia- 

 tions which are now referred to.^ For not only do we 

 find variations of a sort which we may call coincident, — 

 in this case variations in the flexibility of the muscles 

 whereby greater movement and control are possible, — but 

 also in the shape of the beak. And if the other utilities 

 spoken of be real, possibly also variations in the claws and 



1 A very comical exhibition of the amount the parrot can raise the upper 

 mandible is seen when he yawns, 



2 It illustrates the method of such correlation in any case. 



