lu ■ 



3 



24 LAWS OF VARIATION. Chap. XXV. 



to diminish the feet, the beak becoming at the same time through 

 correlation shorter ; but that in those few breeds in which length 

 of beak has been a selected point, the feet, notwithstanding 

 disuse, have through correlation increased in size. 



With the increased length of the beak in pigeons, not only 



the tongue increases in length, but likewise the orifice of 

 nostrils. But the increased length of the orifice of the nostrils 

 perhaps stands in closer correlation with the development of 

 the corrugated skin or wattle at the base of the beak ; for 

 when there is much wattle round the eyes, the eyelids are greatly 

 increased or even doubled in length. 



There is apparently some correlation even in colour be- 

 tween the head and the extremities. Thus with horses a large 

 white star or blaze on the forehead is generally accompanied by 

 white feet. 8 With white rabbits and cattle, dark marks often 

 co-exist on the tips of the ears and on the feet. In black and tan 

 dogs of different breeds, tan-coloured spots over the eyes and 

 tan-coloured feet almost invariably go together. These latter 

 cases of connected colouring may be due either to reversion or 

 to analogous variation, — subjects to which we shall hereafter 

 return, — but this does not necessarily determine the question of 

 their original correlation. If those naturalists r are correct who 

 maintain that the jaw-bones are homologous with the limb-bones 

 then we can understand why the head and limbs tend to vary 

 together in shape and even in colour; but several highly com- 

 petent judges dispute the correctness of this view. 



The lopping forwards and downwards of the immense ears of 

 fancy rabbits is in part due to the disuse of the muscles and 

 in part to the weight and length of the ears, which have been 

 increased by selection during many generations. Now, with 

 the increased size and changed direction of the ears, not only 

 has the bony auditory meatus become changed in outline, 



direction, and greatly in size, but the whole skull has been 

 slightly modified. This could be clearly seen in " half-lop 

 that is, in rabbits with one ear alone lopping forward — for the 

 opposite sides of their skulls were not strictly 

 This seems to me a curious instance of correlation, between hard 



sym 



8 « The Farrier and Naturalist,' vol. i., 1828, p. 456. 



