20 BIOLOGICAL SOCIETY OF WASHINGTON. 



But Darwin, like most other thorough naturalists, was little 

 satisfied with the L,amarckian theory, because it left, as all 

 now admit, so much still unexplained, but instead of reject- 

 ing it in toto, as most other naturalists did, he sought, and 

 happily succeeded in finding the principle on which the 

 remainder of the facts could be accounted for ; or, at least, 

 the greater part of them, for it seems that however deeply 

 we may probe the secrets of nature there will ever remain a 

 few residual phenomena that refuse to submit to our canons. 



It is certainly unnecessary that I should occupy your time 

 with any extended exposition of the law of selection, and I 

 will content myself with the following bare definitions : 



Natural selection is the general law that variations are con- 

 stantly occurring in organized beings, and that such of these 

 variations as prove advantageous to the species are preserved 

 through heredity and transmitted to posterity while those 

 which are not advantageous or are disadvantageous to the 

 species are not preserved nor transmitted ; the cause of such 

 selection being the fact that advantageous variations tend to 

 increase the chances that the individuals possessing them will 

 reach the reproductive age and continue longer to reproduce, 

 and will hence leave a larger number of offspring than those 

 individuals which had not varied or had varied in an equivo- 

 cal or unfavorable manner. 



Artificial selection is the act of man in intelligently select- 

 ing the individuals that possess in the highest degree the 

 particular qualities that he desires to produce as the parents 

 of the animals or plants which he wishes to domesticate or 

 cultivate. The eminent success obtained by man in this way 

 is the certain proof that the qualities of the parents are trans- 

 mitted to their offspring, and explains the efficacy of natural 

 selection. 



