402 ON SUPPOSED BOTANICAL PROOFS OF [VII. 



and breaks down as soon as it is critically examined. I believe 

 that I shall be able to prove that correlation cannot be used as 

 the indirect proof of an hypothesis, of which all direct evidence 

 is still completely wanting. It must not be forgotten that the 

 onus probandi rests with my opponents : they defend the asser- 

 tion that acquired characters can be transmitted, and they ought 

 therefore to bring forward actual proofs ; for the mere fact that 

 the assertion has been hitherto accepted as a matter of course 

 by almost every one, and has only been doubted by a very few 

 (such as His, du Bois-Reymond, and Pfliiger), cannot be taken 

 as any proof of its validity. Not a single fact hitherto brought 

 forward can be accepted as a proof of the assumption. Such 

 proofs ought to be found : facts ought to be discovered which 

 can only be understood with the aid of this hypothesis. If, for 

 instance, it could be shown that artificial mutilation sponta- 

 neously re-appears in the offspring with sufficient frequency 

 to exclude all possibilities of chance, then such proof would 

 be forthcoming. The transmission of mutilations has been 

 frequently asserted, and has been even recently again brought 

 forward, but all the supposed instances have broken down 

 when carefully examined. I think I may here safely omit all 

 further reference to the proofs dependent upon transmitted 

 mutilations, especially as Doderlein ^ has already, in the most 

 convincing manner, disposed of the argument derived from the 

 tailless cats which were so triumphantly exhibited at the last 

 meeting of the Association of German Naturalists^. 



I now come to the real subject of this paper — the supposed 

 botanical proofs of the transmission of acquired changes. The 

 botanist Detmer has recently brought forward certain pheno- 

 mena in vegetable ph3'-siology^, as a support for the transmission 

 of such changes, and although I do not believe that they will 

 bear this interpretation, the discussion of them may perhaps be 

 useful. I am even inclined to think that these and a few other 

 phenomena in vegetable physiology, upon which I shall also 

 touch, are very likely to throw new light upon the whole ques- 

 tion which has been so frequently misunderstood. I should 



1 See ' Biol. Centralbl' Bd. VII. No. 23. 

 ^ See the next Essay (VIII). 



^ Detmer, ' Zum Problem der Vererbung,' Pfliiger's Archiv f. Physio- 

 logic, Bd. 41, (1887), p. 203. 



