Chap. I.] VARIATION UNDER DOMESTICATION. 13 



and goats in countries where they are habitually 

 milked, in comparison with these organs in other 

 countries, is probably another instance of the effects of 

 use. Not one of our domestic animals can be named 

 which has not in some country drooping ears ; and the 

 view which has been suggested that the drooping is due 

 to disuse of the muscles of the ear, from the animals 

 being seldom much alarmed, seems probable. 



Many laws regulate variation, some few of which can 

 be dimly seen, and will hereafter be briefly discussed. 

 I will here only allude to what may be called correlated 

 variation. Important changes in the embryo or larva 

 will probably entail changes in the mature animal. In 

 monstrosities, the correlations between quite distinct 

 parts are very curious ; and many instances are given 

 in Isidore Geoffroy St. Hilaire's great work on this 

 subject. Breeders believe that long limbs are almost 

 always accompanied by an elongated head. Some 

 instances of correlation are quite whimsical : thus cats 

 which are entirely white and have blue eyes are 

 generally deaf; but it has been lately stated by Mr. 

 Tait that this is confined to the males. Colour and 

 constitutional peculiarities go together, of which many 

 remarkable cases could be given amongst animals and 

 plants. From facts collected by Heusinger, it appears 

 that white sheep and pigs are injured by certain plants, 

 whilst dark-coloured individuals escape : Professor Wy- 

 man has recently communicated to me a good illustra- 

 tion of this fact ; on asking some farmers in Virginia 

 how it was that all their pigs were black, they informed 

 him that the pigs ate the paint-root (Lachnanthes), which 

 coloured their bones pink, and which caused the hoofs 

 of all but the black varieties to drop off ; and one of the 



