THEORIES OF LAMARCK AXD DARWIN 369 



account for evolution, up to the announcement of the muta- 

 tion-theory of De \>ies in 1900, three in particular had 

 commanded the greatest amount of attention and been the 

 field for varied and extensive discussion. These are the 

 theories of Lamarck, Darwin, and Weismann. They are 

 comprehensive theories, dealing with the process as a whole. 

 Most of the others are concerned with details, and emphasize 

 certain phases of the process. 



Doubtless the factors that have played a part in molding 

 the forms that have appeared in the procession of life upon 

 our globe have been numerous, and, in addition to those that 

 have been indicated, Osbom very aptly suggests that there 

 may be undisco\'ered factors of e^'olution. Within a few 

 years DeVries has brought into prominence the ideaof sudden 

 transformations leading to new species, and has accounted 

 for organic evolution on that basis. Further consideration of 

 this theory, hov/ever, will be postponed, while in the present 

 chapter we shall endeavor to bring out the salient features 

 of the theories of Lamarck and Darwin, without going into 

 much detail regarding them. 



Lamarck 



Lamarck was the first to give a theory of evolution that 

 has retained a place in the intellectual world up to the present 

 time, and he may justly be regarded as the founder of thai 

 doctrine in the modern sense. The earlier theories were 

 more restricted in their reach than that of Lamarck. Eras- 

 mus Darwin, his greatest predecessor in this held of thought, 

 announced a comprehensive theory, which, while suggestive 

 and forceful in originality, was diffuse, and is now only of 

 historical importance. The more prominent writers on evo- 

 lution in the period ])rior to Lamarck will ])e dealt with in 

 the chapter on the Rise of Evolutionary Thought. 

 24 



