CHAP. I.J VARIATION UNDER DOMESTICATION, 9 



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 communicated to me a good 

 illustration of this fact ; on asking some fanners 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 " (i.e. Virginia squatters) added, "we 

 select the black members of a litter for raising, as they alone have 

 a good chance of living." Hairless 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 select- 

 ing, 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 well 

 worth while carefully to study the several treatises on some of our 

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

 etc. ; and it is really surprising to note the endless points of struc- 

 ture 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 import- 

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

 is the fullest and the best on this subject. No breeder doubts how 

 strong is the tendency to inheritance ; that like produces like is his 

 fundamental belief : doubts have been thrown on this principle only 

 by theoretical writers. When any deviation of structure often ap- 

 pears, and we see it in the father and child, we cannot tell whether 

 it may not be due to the same cause having acted on both ; but 

 when amongst individuals, apparently exposed to the same condi- 

 tions, any very rare deviation, due to some extraordinary combina- 

 tion of circumstances, appears in the parent say, once amongst 

 several million individuals and it reappears in the child, the mere 

 doctrine of chances almost compels us to attribute its reappearance 

 to inheritance. Every one must have heard of cases of albinism, 

 prickly skin, hairy bodies, etc., appearing in several members of the 

 same family. If strange and rare deviations of structure are really 

 inherited, less strange and commoner deviations may be freely 

 aclmi tted to be inheritable. Perhaps the correct way of viewing the 



