388 ON THE SUPPOSED BOTANICAL PROOFS OF THE 



moisture, and that combination of different influences which we 

 call climate. All these, with use and disuse, may perhaps produce 

 great effects upon the body (soma) of the individual, but cannot 

 produce any effect in the transformation of the species, simply 

 because they can never reach the germ-cells from which the 

 succeeding generation arises. But if as it seems to me the 

 facts of the case compel us to reject the assumption of the trans- 

 mission of acquired characters, there only remains one principle 

 by which we can explain the transformation of species the 

 direct alteration of the germ-plasm, however we may imagine that 

 such alterations have been produced and combined to form useful 

 modifications of the body. 



The difficulty of understanding these processes of transformation 

 is by no means lightened by abandoning the Lamarckian theory. 

 The difficulty in fact becomes much greater, for we are now com- 

 pelled to seek a different explanation of many phenomena which 

 were previously believed to be understood. But this can hardly be 

 regarded as a reason for not accepting the view : for we are in 

 want of a correct explanation rather than one which is easy and 

 convenient. We seek truth, and when we recognize that our 

 path is leading in a wrong direction, we must leave it and take 

 another road even if it presents more difficulties. 



My theory rests, on the one hand, upon certain theoretical con- 

 siderations which will be mentioned below, and which I have 

 attempted to develope in previous papers l . On the other hand, it 

 rests upon the want of any actual proof of the transmission of acquired 

 characters. My theory might be disproved in two ways, either 

 by actually proving that acquired characters are transmitted, or by 

 showing that certain classes of phenomena admit of absolutely 

 no explanation unless such characters can be transmitted. It 

 will be admitted, however, that we must be very cautious in 

 accepting proofs of this latter kind, for the impossibility of ex- 

 plaining a given phenomenon may be merely temporary, and may 

 disappear with the progress of science. No one could have explained 

 the useful adaptations so common in animals and plants, before the 



1 Consult 'Ueber die Vererbung,' Jena, 1883; 'Die Kontinuitiit des Keim- 

 pla8trias,' Jena, 1885 ; ' Ueber die Zahl der Richtungskorper und iiber ihre Bedeu- 

 tung fur die Vererbung,' Jena, 1887. These papers are translated as the second, 

 fourth and sixth Essays in the present volume. 



