A NEW THEORY OF TitE ORIGIN OF SPECIES. 509 



We can not deny that variation exists. Living forms have not the 

 rigidity of stone; they vary incessantly, and these variations have 

 been used b}^ breeders for the creation of races. Modifications of this 

 kind are restricted, however, within certain limits. Their amplitude is 

 restrained b\' three conditions, as follows: Generalh" they are not per- 

 manent and they disappear at the same time as do the circumstances 

 under which they are produced; they are not transmissible by gener- 

 ation to descendants; and finally, the modified beings have not lost the 

 aptitude of crossing with those that have not been modified^ This is 

 what is meant by declaring that these individual variations can not 

 create a new species; for these three defects found in the modified 

 being are exactl}' those which define a species. 



Up to the i)resent time no one has ever seen an animal or vegetable 

 species engender another or transform itself into another. In other 

 terms, no one, except perhaps Hugo de Vries, has perceived a living 

 form arising from another form, yet differing from it by features hav- 

 ing the value of those which distinguish species, and showing itself 

 inapt for crossing with the parent, although capable of maintaining 

 and preserving itself by generation. Such a profound transformation 

 can not be accomplished in a moment or by a single effort. 



Darwin supposed that such a transformation could be accomplished 

 by degrees. According to his view the cumulative repetition of certain 

 small variations might effect a more considerable transformation. In 

 order to do this it would suffice that they should always be produced 

 in the same direction during a long course of generations. Breeders 

 effect this by reproducing and maintaining the conditions of the origi- 

 nal transformation and breeding together the individuals which present 

 such transformation. This is "artificial selection." It is a judicious 

 and methodical exercise of the two properties of heredity and of variation 

 practised for the interest and advantage of man. 



The supposition of Darwin is equivalent to admitting that nature, 

 personified, acts like man, heedful of consequences and with a method, 

 by "natural selection" having in view the interest and advantage of 

 species. Certain slight variations appearing under diverse influences, 

 for example, under a change in the environment, will constitute an 

 advantage for individuals. Such individuals are thus l)etter adapted 

 to these new circumstances and have a better chance of survival; these 

 are the ones which will pair and h}- heredity preserve the advanta- 

 geous variation, fix it, accumulate it, until there is formed a race, a 

 variety, and finally a new species. This automatic play of the best 

 adaptation favoring certain individuals, permitting them to survive 

 and to reproduce themselves, has here, in natural selection, the same 

 pr;)vidential role as the breeder plays in artificial selection. It is the 

 best adaptation which designs and choo.-es the useful variation: it is 

 that which favors the individuals that possess it; it is that, in line. 



