Chap. I.] VARIATION UNDER DOMESTICATION. 9 



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, tbe 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 Wyman has recently com- 

 municated to me a good illustration 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 " crackers " 

 (*. e. Virginia squatters) added, " we select the black members of a 

 litter for raising, as they alone have a good chance of living." Hair- 

 less dogs have imperfect teeth : long-haired and coarse-haired 

 animals are apt to have, as is asserted, long or many horns ; pigeons 

 with feathered feet have skin between their outer toes ; pigeons 

 with short beaks have small feet, and those with long beaks large 

 feet. Hence if man goes on selecting, and thus augmenting, any 

 peculiarity, he will almost certainly modify unintentionally other 

 parts of the structure, owing to the mysterious laws of correlation. 



The results of the various, unknown, or but dimly understood 

 laws of variation are infinitely complex and diversified. It is weD 

 worth while carefully to study the several treatises on some of 

 our old cultivated plants, as on the hyacinth, potato, even the 

 dahlia, &c. ; and it is really surprising to note the endless points of 

 structure and constitution in which the varieties and sub-varieties 

 differ slightly from each other. The whole organisation seems to 

 have become plastic, and departs in a slight degree from that of the 

 parental type. 



Any variation which is not inherited is unimportant for us. 

 But the number and diversity of inheritable deviations of structure, 

 both those of slight and those of considerable physiological impor- 

 tance, are endless. Dr. Prosper Lucas's treatise, in two large 

 Volumes, is the fullest and the best on this subject. IsTo breeder 



