Summarising we see, that some of van Iterson's 

 objections to Blackman's theory are not so serions as 

 lie tlîought tliem to be, while on the other liand several 

 reasons can be adduced in explanation for tlie déviations 

 found in his investigation. 



As only van Iterson's results stand against Blaclc- 

 man's theory and ail other processes so far investigated, 

 more or less agrée with it, I do not think it advisable to 

 reject Blackman's theory. 



Since the publication of the foregoing considérations a 

 second paper of van I ter son and Miss van Amstel ') 

 has appeared, in which the conclusion that Bl ackman's 

 theory has to be rejected is defended against my objections. 



I advanced three arguments, why I thought this con- 

 clusion not justified by the authors' results. The three 

 reasons, which might be the cause that Blackman's 

 theory was not applicable to the results obtained in the 

 cases of sugar-inversron and alcoholic fermentation were: 



1°. The living organism is no homogeneous System. 



2°. Even in vitro van 't Hoff's law has only approxi- 

 mate value in some cases. 



30. Since in many cases in plant-physiology the favour- 

 able influence of higher températures does not 

 make itself felt at once, perhaps hère too such a 

 time-factor may play a part. 



In answering thèse three points, van Iterson begins 

 with the last one; and the greater part of his paper 

 bears on the discussion of this point. Now I want to 

 emphasize that this point has had a very subordinate 

 place in my argument; lonlysaid: „finally the possibility 

 is not excluded, that the favourable influence of high 



1) G. van Iterson Jr. and Miss J. van A m s tel. II. 1910. 



