386 BIOLOGY AND ITS MAKERS 



of his, writings and had incidentally corrected several d 

 neons conception. 



Neo-Lamarckism. — The ideas of Lamarck regarding the 

 beginning of variations. have been revived and accorded much 

 respect under -the designation of Neo-Lamarckism. The 

 revival of :Lamarckjsm is especially owing to the palaeon- 

 tological investigation's of Cope and Hyatt. The work of 

 E. D. Cope in particular, led him to attach importance to the 

 effect of mechanical and other external causes in producing 

 variation, and* he points out many instances of use-inher- 

 itance. Neo-Lamarckism has a considerable following; it 

 is a revival of the fundamental ideas of Lamarck. 



Darwin's Theory 



While Lamarck's theory rests upon two sets of facts, 

 Darwin's is founded on three: viz., the facts of variation, 

 of inheritance, and of natural selection. The central feature 

 of his theory is the idea of natural selection. No one else 

 save Wallace had seized upon this feature when Darwin 

 made it the center of his system. On account of the part 

 taken by Wallace simultaneously with Darwin in announcing 

 natural selection as the chief factor of evolution,, it is appro- 

 priate to designate this contribution as the Darwin-Wallace 

 principle of natural selection. The interesting connection 

 between the original conclusions of Darwin and Wallace is 

 set forth in Chapter XIX. 



Variation. —It will be noticed that two of. the causes 

 assigned by Darwin are the same . as those designated by La- 

 marck, but their treatment is quite different. Darwin (Fig. 

 1 13) assumed variation among animals and plants without at- 

 tempting to account for it, while Lamarck undertook to state 

 the particular influences which produce variation, and al- 

 though we must admit that Lamarck was not entirely sue- 



