( 599 ) 
has lost the function, it was possible from each of these + curves to 
calculate the curve which would have occurred if the temperature 
had not exerted a (lasting) noxious influence. Indeed, by these 4 
ways was actually obtained the same curve, showing a pronounced 
optimum and forming the continuation of the simple curve found 
for harmless temperatures for the 4 fore-heating periods. It should 
besides be noticed that also the velocities above the noxious tempe- 
rature were first measured after the ‘‘Antrieb’’ was finished, which 
proved to be the case when about 20 eM? CO, had evolved. 
We think that from these results the conclusion must be drawn 
that the theory of DucLAux-BLACKMAN should be rejected, for after 
this theory, when po injury of the active agent by the high tem- 
perature was occasioned, the relation between velocity and tempera- 
ture would be represented by a continuously rising curve, and its 
growing concave beneath, as well as its falling above the opti- 
mum would be caused by the injury of the active agent during the 
fore-heating. 
Against this conclusion now Mr. RuvutGrrs advances in the first 
place the following : 
In his researches the praesentation time wanted for the perception 
of the gravity by coleoptiles of oat-germplants for temperatures of 
0°, 5°, 10°, 20°, and 25°C. proved to be independent of the time 
of fore-heating (the successive fore-heating periods differed at least 
1 hour from each other). At 30° C., however, the praesentation 
time proved to decrease with the time of fore-heating ; after about 
12 hours, the shortest praesentation time was attained which, after 
24 hour’s fore-heating was still maintained. On the other hand, above 
30° the praesentation time ¢rcreased with continuation of the fore- 
heating: at 35°C. it attained a maximum after 18 hours, which it 
had still preserved after 24 hours; at 37° and 38° C. however, it 
increased continuously, as long as the fore-heating was continued 
to 24 hours). 
We should bear in mind that the praesentation time cannot be com- 
pared with the velocity of a process, but to a certain extent to the 
reciprocal value of a velocity. So the curve “praesentation time-tem- 
perature’ shows a “temperature minimum” (with a slight difference 
only for the different periods) of fore-heating instead of a “tempe- 
rature optimum”. 
From the fact that at 30° C. at first a greater value for the 
praesentation time is found, which decreases with continuation of 
foreheating, Rurcers coneludes that the higher temperature only 
reaches its full. favorable influence after a prolonged remaining 
39* 
