Ir THE ORIGIN OF SPECIES 41 
-same direction ; while, in the other, no race was 
_eyolyed, because no such selection was exercised, 
_A race is a propagated variety ; and as, by the laws 
of reproduction, offspring tend to assume the 
/ parental forms, they will be more likely to pro- 
'pagate a variation exhibited by both parents than 
that possessed by only one. 
There is no organ of the body of an animal 
which may not, and does not, occasionally, vary 
_ more or less from the normal type; and there is no 
variation which may not be transmitted and which, 
if selectively transmitted, may not become the 
- foundation of a race. This great truth, sometimes 
_ forgotten by philosophers, has long been familiar 
_ to practical agriculturists and breeders ; and upon 
it rest all the methods of improving the breeds of | 
- domestic animals, which, for the last century, have 
been followed with so much success in England. 
Colour, form, size, texture of hair or wool, pro- 
_ portions of various parts, strength or weakness of 
constitution, tendency to fatten or to remain lean, 
to give much or little milk, speed, strength, tem- 
per, intelligence, special instincts; there is not one 
of these characters the transmission of which is not 
an every-day occurrence within the experience of 
cattle-breeders, stock-farmers, horse-dealers, and 
dog and poultry fanciers. Nay, it is only the other 
day that an eminent physiologist, Dr. Brown- 
Séquard, communicated to the Royal Society his 
discovery that epilepsy, artificially produced in 
