CHAPTER XI 

 INHERITANCE OF ACQUIRED CHARACTERS 



Tout ce qui a ete acquis, trace ou change dans Torganisation des 

 individus, pendant le cours de leur vie, est conserve par la generation 

 et transmis aux nouveaux individus qui proviennent de ceux qui ont 

 eprouve ces changements. — Lamarck. 



Heaven forfend me from Lamarck nonsense of a tendency to pro- 

 gression, adaptation from the slow willing of animals, etc. ; but the 

 conclusions I am led to are not wholly different from his, though the 

 means of change are wholly so. — DAmviN to Hooker, 1848. 



The "fourth Law of Evolution," as expressed by Lamarck 

 in his "Zoological Philosophy," reads as follow^s: "All that has 

 been acquired, begun, or changed in the structure of individuals 

 in their lifetime, is preserved in reproduction and transmitted to 

 the new individuals which spring from those which have in- 

 herited the change." 



This principle was used by Lamarck as one of the funda- 

 mental elements in his theory of the transmutation of species. 

 For nearly a hundred years it attracted little attention, being 

 accepted as a part of the law of heredity by most persons, even 

 by those most opposed to the essential part of Lamarck's theory, 

 the derivation or transmutation of species. Among others, 

 Darwdn accepted it as one of the factors in evolution of forms. 

 With Herbert Spencer it became one of the fundamental prin- 

 ciples of the philosophy of Evolution. Mr. Spencer states tlie 

 proposition in this way: "Change of function produces change 

 of structure: it is a tenable hypothesis that changes of structure 

 so produced are inherited." For the supposed inheritance of 

 characters produced by the impact of environment or by 

 resultant activities of the individual the term progressive 

 heredity has been devised. The fact of the existence of pro- 



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