CHAPTEK VI 



EXPLANATORY HYPOTHESES 



I WILL next state shortly, but as fairly as I can, the 

 principal hypotheses known to me , which have been 

 put forwards as explanations of the facts given in the 

 last chapter. 



Lamarck (1809) was the first person with a com- 

 petent knowledge of botany and zoology, who tried 

 to solve the problem of the transmutation of species. 

 He supposed that the changes in the environment, 

 which were constantly taking place, gave rise (1) 

 among the higher animals to new wants or needs, 

 which caused the employment of organs in different 

 ways, for new actions would be necessary in adap- 

 ting themselves to new circumstances. This gave 

 rise to the greater or less use of these organs. Use 

 gradually strengthens an organ, develops and en- 

 larges it ; while disuse weakens it , causes it to 

 become reduced, until finally it disappears. (2) 

 With plants and the lower animals he taught that 

 change in climate and in the nature of the food acted 

 directly on the organisms, changing them also. (3) 

 These changes, he said, brought about by use or by 

 the long continued action of the environment, would 

 in time be transmitted to future generations, and so 



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