422 THE SUPPOSED TRANSMISSION OF MUTILATIONS. 



instance, the degeneration of the eyes of animals inhabiting- caves 

 or the sunless depths of lakes or the sea. 



But it is obvious that such an explanation tacitly assumes that 

 changes produced by use or disuse can be transmitted to the 

 offspring ; it assumes the transmission of acquired characters. 



Lamarck made this assumption as a matter of course, and when 

 half a century later Charles Darwin, his more fortunate successor, 

 refounded the theory of organic evolution, he also believed that we 

 could not entirely dispense with the Lamarckian principle of 

 explanation, although he added the new and extremely far-reaching 

 principle of natural selection. But he certainly attempted to decide 

 whether the Lamarckian principle of the effects of use and disuse is 

 truly efficient, by asking himself the question whether such changes, 

 as for example those produced by exercise during an individual 

 life, can be transmitted to the offspring. Many observations ap- 

 peared to hjm, if not to prove the transmission directly, yet to 

 render it extremely probable ; and he thus came to the conclusion that 

 there is no sufficient reason for denying the transmission of acquired 

 changes. Hence, in Darwin's works, use and disuse still play 

 important parts as direct factors of transformation, in addition to 

 natural selection. 



Darwin was not only an original genius, but also an extra- 

 ordinarily unbiassed and careful investigator. Whatever he ex- 

 pressed as his opinion had been carefully tested and considered. 

 This impression is gained by every one who has studied Darwin's 

 writings, and perhaps it in part explains the fact that doubts as to 

 the correctness of the Lamarckian principle adopted by him have 

 only arisen during the last few years. These doubts have, however, 

 culminated in the decided denial of the assumption that changes 

 acquired by the body can be transmitted. I for one frankly admit 

 that I was in this respect under the influence of Darwin for a long 

 time, and that only by approaching the subject from an entirely 

 different direction was I led to doubt the transmission of acquired 

 characters. In the course of further investigations I gradually 

 gained a more decided conviction that such transmission has no 

 existence in fact. 



Doubts on this point have been expressed not only by me but 

 also by others, such as du Bois-Reymond and Pfliiger. Indeed, 

 concerning a certain class of acquired characters, viz. mutilations, 



