LAMARCK AND HIS THEORY 19 



the inheritance of acquired characters. This we shall consider 

 further. 



Regarding Lamarck's later life, Osborn (p. 158) says: 



His devotion to the study of the small forms of life, probably with in- 

 ferior facilities for work, for he was extremely poor, gradually deprived him 

 of the use of his eyes, and in 1819 he became completely blind. The last 

 two volumes of the first edition of his Natural history of invertehrated 

 animals, which was begun in 1816 and completed in 1822, was carried on 

 by dictation to his daughter, who showed him the greatest devotion; after 

 Lamar.ck was confined to his room, it is said she never left the house. 

 Lamarck was thus saddened in his old age by extreme poverty and by the 

 harsh reception of his transmutation theories, in the truth of which he 

 felt the most absolute conviction. 



Lamarck's Theory 



The factors recognized by Lamarck as concerned in evolu- 

 tion may be summarized as follows : — 



1. The direct effect of environment. We know that a plant 

 in rich soil grows large and luxuriant, but that the same plant 

 in poor soil would remain small and stunted. This is a direct 

 effect of the environment. Lamarck supposed that such 

 effects of environment are cumulative from generation to 

 generation so that long-continued growing in rich soil would 

 produce a more luxuriant race, while continued growing in 

 poor soil would produce a different and smaller race. In the 

 case of animals Lamarck does not think that the action of 

 environment is quite so direct, but that animals are changed 

 indirectly through changes in their habits. Buff on considered 

 the action of environment direct in both animals and plants, 

 and this view Darwin seems to have adopted rather than 

 Lamarck's slightly different one. Darwin in his Variation 

 adopts this factor, the direct effect of environment, as one of 

 the causes, if not the chief cause of variations. He says 

 (p. 6): 



If then organic beings in a state of nature vary even in a slight degree, 

 owing to changes in the surrounding conditions, of which we have abundant 

 geological evidence, or from any other cause, — then the severe and often- 

 recurrent struggle for existence will determine that those variations, how- 

 ever slight, which are favorable shall be preserved or selected, and those 

 which are unfavorable shall be destroyed. 



