29 
though it seems a great deal slighter than with the Phycomyces- 
cells. 
VI. After it had already appeared in the research on the adaptation 
to dark, that the sensitiveness to light being in 64 M.C. is 350.000 
times less than in the dark, we could further consider the course 
of adaptation when the cell has been previously adapted to fainter 
or stronger light. For the present however we had to restrict our- 
selves to the question: How much changes the tone or degree of 
sensitweness, when the cells have been adapted to different intensities 
of light? 
Experiments. After a stay of at least 2 hours in different intensities 
it was determined, what quantity of light was just able to call 
forth a light-growth-response, while the cells remain in that inten- 
sity. In Table V the result of these experiments is briefly summarized. 
TABLE V. Proportion of sensitiveness after adaptation 
to different intensities, 
Adapted to Limit Set Sanaa 
64 M.C. 3000—4000 M.C.S. 1 
Bad 200— 400, 8,75—11,5 
ak ee 10—140 
le 05 aanne 580—1160 
ae O4 08 4315—8750 
hakt ie 17.500—35.000 
Dark Pool, + 350.000 
Now it appears, that for intensities of '/,, M.C. to 8 M.C. the 
sensitiveness decreases proportionally to the intensity to which the 
cell has been adapted. In 64 M.C. the sensitiveness seems to have 
lessened still more than would be expected according to this rule. 
To the very lowest intensities this rule could not hold good, because 
then the sensitiveness would become infinitely great in the dark. 
So we see after all that in '/,,, M.C. the sensitiveness in comparison 
with '/,, has not increased 8 times, but only 4 times more. Yet it 
is already striking that it holds good to '/,, M.C. 
One would be inclined to simply accept that one had to deal 
here with the law of Weger. Yet we should be careful in making 
a comparison. We have here the very elementary case of one single 
cell, for which we have demonstrated as follows: 
