Correlation 
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 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’ (ze. 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 selecting, and thus 
augmenting, any peculiarity, he will almost cer- 
tainly modify unintentionally other parts of the 
structure, owing to the mysterious laws of the 
correlation of growth.” 
The great importance of the principle of the 
correlation of organs is, that natural selection 
may indirectly cause the survival of unfavourable 
variations, or of variations which are of no 
utility to the organism, because they happen to 
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