526 ZOOLOGY 



2 . That at some time life appeared on the earth, from non-life, 



a. Suddenly, much as it is at present. 



b. Gradually, starting in simple form and becoming 

 complex as at present. 



Two fundamental questions are here : Did life start de novo at 

 some time? Has it remained constant since it started? 

 Another has arisen since: Can life start anew at present {spon- 

 taneous generation) ? 



John Ray about 1725 crystallized and gave formal support 

 to the idea held by Linnaeus and many of his predecessors that 

 organisms arose de novo, by special creation, and since that time 

 have remained practically constant. Cuvier also gave this view 

 the support of his influence. Lamarck (i 774-1829) contended 

 that species were changeable, that the fossils in the strata were 

 remains of extinct species which were the ancestors of the present 

 ones. He held that the needs of the organism resulting in the 

 use and disuse of organs, and the action of the environment upon 

 the organism changed individuals and that these modifications 

 were transmitted in some measure to the next generation. Thus 

 he thought evolution occurred. He was the founder of the 

 evolution theory in its modern sense and made an effort to put 

 it on a rational basis. 



Charles Darwin (1809-1882), accepting essentially La- 

 marck's views, added to them the principle of natural selection 

 (§137) through the struggle for existence and the elimination 

 of the unfit. This was his great contribution. It was so rea- 

 sonable and he supported it with such an array of facts that it 

 put the evolution idea on a firm footing and stimulated bio- 

 logical thought and investigation more perhaps than any other 

 suggestion ever proposed. A. R. Wallace shares with Darwin 

 the honor of discovering the idea of natural selection, although 

 the latter's statement was theoretical rather than experimental. 



With the work of Darwin the idea of the variability of species 

 may be said to have been generally accepted by scientists. 

 The questions now came to hinge upon the method of origin of 

 the variations and their transmissibility to new generations. 



August Weismann (1834-1915) held that body characters, 

 gained as Lamarck suggested by use and disuse of the body. 



