THEORIES OF HEREDITY AND VARIATION. 5 1 



ever, by gathering a large amount of statistics, proved that, among 

 Jews, children are not infrequently born wholly or partly circum- 

 cised. This appears to be due to the continued repetition of the 

 same mutilation generation after generation. 



lamarck's laws. 



Although Aristotle was the first to advance the theory that 

 acquired characters become congenital characters in succeeding 

 generations, the theory of such transference as an explanation of 

 variations was not fully stated and explained until done so by 

 Lamarck, a French philosopher, in his " Philosophic Zoologique," 

 published in 1809. The statement of his theory may be best given 

 by quoting his third and fourth laws : 



third law. 



The development of organs and their force, or power of action, 

 are in direct relationship to the employment of these organs. 



fourth law. 



All that has been acquired or altered in the organization of 

 individuals during their lives is preserved by generation, and trans- 

 mitted to individuals which spring from those which have under- 

 gone these changes. 



At another place Lamarck explains his third law as follows : 

 "In every animal which has not passed the term of its develop- 

 ment, the more frequent and sustained employment of each organ 

 strengthens little by little this organ, develops it, and gives it a 

 power proportional to the length of its employment ; whereas the 

 constant lack of use of the same organ insensibly weakens it, dete- 

 riorates it, progressively diminishes its powers, and ends by causing 

 it to disappear." 



