316 LAWS OF VARIATION. Chap. XXV. 



chapter, we see that in several breeds of the pigeon the length 

 of the beak and the size of the feet are correlated. The view 

 which, as before explained, seems the most probable is, that 

 disuse in all cases tends to diminish the feet, the beak 

 becoming at the same time shorter through correlation ; but 

 that in some few breeds in which length of beak has been a 

 selected point, the feet, notwithstanding disuse, have increased 

 in size through correlation. In the following case some kind 

 of correlation is seen to exist between the feet and beak : 

 several specimens have been sent to Mr. Bartlett at different 

 times, as hybrids between ducks and fowls, and I have seen 

 one ; these were, as might be expected, ordinary ducks in a 

 semi-monstrous condition, and in all of them the swimming- 

 web between the toes was quite deficient or much reduced, 

 and in all the beak was narrow and ill-shaped. 



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

 the tongue increases in length, but likewise the orifice of the 

 nostrils. But the increased length of the orifice of the 

 nostrils perhaps stands in closer correlation with the develop- 

 ment 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 between 

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

 star or blaze on the forehead is generally accompanied by white 

 feet. 9 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 I 

 shall hereafter return, — but this does not necessarily determine 

 the question of their original correlation. Mr. H. W. Jackson 

 informs me that he has observed many hundred white-footed 

 cats, and he finds that all are more or less conspicuously 

 marked with white on the front of the neck or chest. 



9 'The Farrier and Naturalist,' me that about three-fourths of white- 

 vol. i., 1828, p. 456. A gentleman faced horses have white legs. 

 wht hu attended to this point, tells 



