CHAPTER II 



THE INHERITANCE OF ACQUIRED 

 CHARACTERS 



At the basis of genetics lies the fact that variation 

 occurs in all living organisms. It is possible to classify 

 variations in a number of different ways.^ At the out- 

 set it is important to realize the distinction between non- 

 heritable and heritable variations. As for the former, 

 it is usually evident that these originate as responses on 

 the part of the organism to environmental stimuli. Ac- 

 quired characters of this sort, however, are of little sig- 

 nificance in genetics, inasmuch as they are not passed on 

 from parent to offspring. It is the heritable variations 

 that provide the material of genetics; and the origin of 

 these is a matter of considerable controversy. For the 

 most part, they are ascribed to mutation, meaning that 

 their origin is sudden and spontaneous, seemingly unre- 

 lated to environmental stimuli. There is some evidence, 

 however, which suggests that heritable variations may 

 originate as acquired characters. It will be appropriate 

 at this point to discuss the controversy on inheritance of 

 acquired characters. 



The idea of inheritance of acquired characters was 

 first clearly developed by Lamarck in connection with 

 his explanation of evolution, the so-called theory of 

 *' appetency," or the effect of use and disuse. Francis 

 Galton, in 1875, was one of the first to express skepti- 



* A serviceable set of classifications is provided by Babcock and 

 Claussen (i). 



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