OBJECTIONS A GA INS T E VOL UTI.ON. 195 



of adaptation due to changes of climate. Thus, to 

 go no further, "pigs with fleece are to be found on 

 the cold plateaus of the Cordilleras, sheep with hair 

 in the warm valleys of the Madeleine, and hairless 

 cattle in the burning plains of Mariquita." That use 

 and disuse are factors in Evolution is evinced by 

 facts within the experience of everybody, such, for in- 

 stance, as the general development of the body of the 

 athlete, the highly delicate senses of touch and hear- 

 ing of the blind, or the atrophied limb of the paralytic. 



The Lamarckian factors were deemed of little 

 importance by Darwin, but recently they have, with 

 some modifications, come into special prominence 

 in America, and constitute the basis of the new the- 

 ory of Neo-Lamarckism. According to Cope and 

 Hyatt, two of the most prominent exponents of this 

 theory, the Lamarckian factors, especially the activi- 

 ties of animals in their constant endeavor to accommo- 

 date themselves to their environment, have been the 

 chief agencies in producing varieties and species, and 

 consequently, the chief agencies also in the Evolu- 

 tion of higher from lower forms of life. 



Natural selection, or the "survival of the fittest," 

 as Spencer loves to call it, is an abbreviated expres- 

 sion for several well-recognized causes of evolution- 

 ary change. Among the more prominent of these 

 are heredity, variation and struggle for existence. 

 Darwin, however, did not teach, as is sometimes 

 imagined, that natural selection is the sole factor of 

 Evolution, although he did, indeed, contend that it 

 is the chief factor. He frankly admitted, especially 

 in his later works, that it left much unexplained, and 



