The Decisive Experiment 173 
perature, light or darkness, particular substances that are 
nutritive, stimulating or poisonous, infections, immuniza- 
tions, etc., could never afford such incontestable evidence 
against Weismann’s theory, as those investigations which 
employ agents having a very definitely localized action. 
Thus for example Heschenhagen’s researches upon 
the adaptability of the lower fungi to sodium chloride 
have, for the reasons stated, little or no value for the 
refutation of Weismann’s theory, even though they have 
proved that the spores of the mycelium which had 
adapted itself to a strongly concentrated saline solution 
were capable of germinating in concentrations in which 
the spores of a mycelium arising in normal conditions 
were incapable of germinating. The same is true for 
the similar researches carried on by Hunger-Errera, 
DeMeyer, Pulst and Ray upon the inheritance of changes, 
mostly physiological rather than morphological in nature, 
which were brought about in the lower fungi by means 
of concentrated salt solutions, for example by sodium 
chloride or copper sulphate or concentrated sugar solu- 
tions, although these results as well as Heschenhagen’s 
are certainly very interesting from the point of view of 
the adaptability of organisms to their environment. 
Also Hoffman’s researches upon the inheritance of 
variations produced by insufficient nourishment in 
Papaver, Migella, and Argemone,—(a relatively large 
number of atypical flowers) ,— and Schubeler’s researches 
upon the inheritance of the more rapid development of 
barley grains which had been transplanted from the south 
part of Norway to the north part, prove incontrovertibly 
the inheritance of the changes induced in organisms 
through general conditions in their environment, but the 
general influences very probably exerted in those cases also 
