THE DISTRIBUTION OF ANIMALS AND PLANTS 419 



species are the descendants of the earlier? Might not the 

 process have been repeated again and again, so as to give 

 animals of this kind to widely separated areas and successive 

 periods without the slow and precarious methods of continuous 

 evolution and migration ? This apparent inconsistency strikes 

 one constantly in the study of discussions of the theory of 

 derivation in connection with geographical and geological dis- 

 tribution. We constantly find the believers in derivation 

 laboriously devising expedients for the migration of animals 

 and plants to the most unlikely places, when it would seem 

 that they might just as well have originated in those places by 

 direct evolution from lower forms. Those who believe in a 

 separate centre of creation for each species must of course 

 invoke all geological and geographical possibilities for the 

 dispersion of animals and plants ; but surely the evolutionist, 

 if he has faith in his theory, might take a more easy and 

 obvious method, especially when in any case he is under the 

 necessity of demanding a great lapse of time. That he does 

 not adopt this method perhaps implies a latent suspicion 

 that he must not repeat his miracle too often. He also per- 

 ceives that if repeated and unlimited evolution of similar 

 forms had actually occurred, there could have remained little 

 specific distinctness, and the present rarity of connecting links 

 would not have occurred. Further, a new difficulty would 

 have sprung up in the geographical and geological relations of 

 species and genera, which would then have assumed too much 

 of the aspect of a preconceived plan. It is only fair to a 

 well-known and somewhat extreme European evolutionist, 

 Karl Vogt, to state that he launches boldly into the ocean of 

 multiple evolution, not fearing to hold that identical species 

 of mollusks have been separately evolved in separate Swiss 

 lakes, and that the horse has been separately evolved in 

 America and in Europe, in the former along a line beginning 

 with Eohippus, and in the latter along an entirely separate line, 



