EVIDENCES OF ORGANIC EVOLUTION 33 



that, for instance, in the hand of a man, the paw of a 

 dog, the wing of a bat, and the paddle of a whale, 

 almost identically the same series of bones can be 

 traced. An obvious explanation is to be found in the 

 supposition that these parts have arisen by the 

 divergent modification of parts which were originally 

 identical. 



4. GEOGRAPHICAL DISTRIBUTION. Observation 

 shows that groups of closely allied creatures are often 

 found living in neighbouring districts, and that when 

 such a barrier as an ocean or a range of lofty moun- 

 tains is passed an entirely new fauna and flora are 

 usually to be met with. These facts may be explained 

 by the hypothesis that allied groups of species origi- 

 nated by a process of descent in the same countries 

 which they now inhabit, and they can be explained 

 by no other known hypothesis. The alternative sup- 

 position that each species was specially created and 

 placed in the locality in which it was best adapted 

 to dwell is singularly in disagreement with the well- 

 known facts that animals and plants transported into 

 entirely new regions often thrive better than in their 

 original homes. The examples of rabbits in Australia 

 and of cardoons and thistles on the Pampas of La 

 Plata are familiar to all from the writings of Darwin. 



5. THE GEOLOGICAL SUCCESSION OF ORGANISMS. 

 The general facts regarding the distribution of allied 

 species of animals and plants in time point in pre- 

 cisely the same direction as those relating to their 

 distribution in space. In a few cases, notably in that 

 of the extinct horse of North America, a long chain of 



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