154 THE ORIGIN OF SPECIES 



been attracted by their six-fingered cousins. In other 

 words, in the one example a race was produced, because, 

 for several generations, care was taken to select both parents 

 of the breeding stock from animals exhibiting a tendency 

 to vary in the same condition ; while, in the other, no race 

 was evolved, because no such selection was exercised. A 

 race is a propagated variety ; and as, by the laws of repro- 

 duction, offspring tend to assume the parental forms, they 

 will be more likely to propagate 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, some- 

 times 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, proportions of various parts, strength or 

 weakness of constitution, tendency to fatten or to remain 

 lean, to give much or little milk, speed, strength, temper, 

 intelligence, special instincts ; there is not one of these 

 characters whose transmission is not an every-day occur- 

 rence 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-Squard, communicated to the Royal Society his 

 discovery that epilepsy, artificially produced in guinea- 

 pigs, by a means which he has discovered, is transmitted 

 to their offspring. 



But a race, once produced, is no more a fixed and immut- 

 able entity than the stock whence it sprang; variations 

 arise among its members, and as these variations are trans- 

 mit ted like any others, new races may be developed out of 

 the pre-existing one ad infinitum, or, at least, within any 

 limit at present determined. Given sufficient time and 

 sufficiently careful selection, and the multitude of races 

 which may arise from a common stock is as astonishing as 

 are the extreme structural differences which they may 

 present. A remarkable example of this is to be found in 

 the rock-pigeon, which Dr. Darwin has, in our opinion, 

 satisfactorily demonstrated to be the progenitor of all our 



