LAMARCK 



the environment becomes very different, it produces 

 in course of time corresponding modifications in the 

 shape and organization of animals. It is true if this 

 statement were to be taken literally, I should be con- 

 victed of an error; for, whatever the environment 

 may be, it does not work any direct modification 

 whatever in the shape and organization of animals. 

 But great alterations in the environment of animals 

 lead to great alterations in their needs, and such alter- 

 ations in their needs necessarily bring about other 

 actions. Now if the new needs become permanent, the 

 animals then adopt new habits which last as long as 

 the needs that evoked them."^ 



Lamarck embodies his doctrine of the inheritance 

 of acquired traits in two laws which are as follows: 



First Law 



In every animal which has not exceeded the limit of its de- 

 velopment, a more frequent and continuous use of any organ 

 gradually strengthens, develops, and enlarges that organ, 

 and gives to it a power proportional to the length of time it 

 has been so used; while the permanent disuse of any organ 

 imperceptibly weakens and deteriorates it, and progressively 

 diminishes its functional capacity, until it finally disappears. 



Second Law 



All the acquisitions or losses wrought by nature on indi- 

 viduals, through the influence of the environment in which 

 their race has long been placed, and hence through the in- 

 fluence of the predominant use or permanent disuse of any 

 organ; all these are preserved by reproduction to the new 

 individuals which arise, provided that the acquired modifica- 



^ Lamarck, op. cit., vol. I, p. 223 [p. 107]. 



C 179 3 



