82 HEREDITY 



ments was based not on any theory of heredity, nor 

 upon any experimental evidence. It was merely 

 advanced as the most feasible explanation that 

 offered itself of the fact of organic evolution. Since 

 his day, however, the cases of apparent inheritance 

 of acquirements have become explicable by the 

 enunciation of the theory of natural selection, 

 which the neo-Darwinians regard as practically the 

 sole factor of organic evolution. Lamarck supposed, 

 for example, that certain antelopes run swiftly 

 because ancestral antelopes, in avoiding their 

 enemies, developed the structures that subserve 

 speed. Natural selection obviously furnishes an 

 adequate explanation of the speed of the antelope 

 we know, and so in innumerable cases. Hence we 

 must look for positive experimental evidence of the 

 inheritance of acquirements, such as cannot be ex- 

 plained by any application of the theory of natural 

 selection. And when we come to inquire, it appears 

 that such evidence is very hard to obtain. The 

 effects neither of single nor of long-continued muti- 

 lations (i.e. mutilations often repeated in successive 

 generations) are found to be inherited. The inherit- 

 ance of acquirements due to use or disuse is un- 

 proved. The inheritance of the effects of changed 

 conditions of life [i.e. changed environment) is 

 dubious. Chalmers Mitchell regards it as uncertain ; 

 Reid as non-existent ; Vernon as proved ; Weismann 

 himself as not proved, for he is able to adduce 

 another explanation of the cases which appear to 

 establish it. Then, again, we find no certainty, even 

 after years of observation, as to the transmission of 

 traumatic epilepsy, i.e. epilepsy due to the infliction 



