434 SUPPOSED TRANSMISSIOY OF MUTILATIONS. [VIII. 



But it is obvious that such an explanation tacitly assumes 

 that changes produced by use or disuse can be transmitted 

 to the offspring ; // 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 wMth 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 

 appeared to him, if not to prove the transmission directly, yet 

 to render it extremel}' probable ; and he thus came to the con- 

 clusion that there is no sufficient reason for denying the trans- 

 mission of acquired changes. Hence, in Darwin's works, use 

 and disuse still play important parts as direct factors of trans- 

 formation, in addition to natural selection. 



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

 ordinarily unbiassed and careful investigator. Whatever he 

 expressed as his opinion had been carefully tested and con- 

 sidered. 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. 



