186 FRAGMENTS OF SCIENCE 



is the impression of the vast amount of labor, both of 

 observation and of thought, implied in its production. 

 Let us glance at its principles. 



It is conceded on all hands that what are called "va- 

 rieties" are continually produced. The rule is probably 

 without exception. No chick, or child, is in all respects 

 and particulars the counterpart of its brother and sister; 

 and in such differences we have "variety" incipient. No 

 naturalist could tell how far this variation could be car- 

 ried; but the great mass of them held that never, by any 

 amount of internal or external change, nor by the mixture 

 of both, could the offspring of the same progenitor so far 

 deviate from each other as to constitute different species. 

 The function of the experimental philosopher is to com- 

 bine the conditions of Nature and to produce her results; 

 and this was the method of Darwin. 1 He made himself 

 acquainted with what could, without any manner of doubt, 

 be done in the way of producing variation. He associated 

 himself with pigeon-fanciers bought, begged, kept, and 

 observed every breed that he could obtain. Though de- 

 rived from a common stock, the diversities of these pigeons 

 were such that "a score of them might be chosen which, 

 if shown to an ornithologist, and he were told that they 

 were wild birds, would certainly be ranked by him as 

 well-defined species." The simple principle which guides 

 the pigeon- fancier, as it does the cattle-breeder, is the 

 selection of some variety that strikes his fancy, and the 

 propagation of this variety by inheritance. With his eye 



1 The first step only toward experimental demonstration has been taken. 

 Experiments now begun might, a couple of centuries hence, furnish data of 

 incalculable value, which ought to be supplied to the science of the future. 



