PHYSIOLOGY: LOEB AND NORTHROP 
457 
temperature, was averaged and this value taken as the average duration 
of Kfe for that temperature. 
Three series of experiments were made. In one the flies were pro- 
vided only with water, in the second with a 1% cane sugar solution, and 
in the third with fermented banana. In the third series the results 
were less regular than in the first two series, probably on account of 
differences in the nature of microorganisms present in the food. We 
intend to repeat these experiments with sterile cultures of flies which 
we are now raising, and will report on these experiments in a later 
publication. 
The following table gives the average duration of Kfe for different 
temperatures. 
DILATION OF LIFE IN DAYS 
TEMPERATURE 
With HzO 
With 1 % 
cane sugar 
34 
2.1 
6.2 
28 
2.4 
7.2 
24 
2.4 
9.4 
19 
4.1 
12.3 
14 
8.3 
9 
11.9 
If we consider the figures for temperatues between 28° and 9° for the 
cultures in water and in sugar we find that there exists a temperature 
coefficient for the duration of life of about the order of magnitude of 
that of chemical reactions, namely, of about 2 for a difference of 10°C, 
We find also that the coefficient is greater for the lower range of tempera- 
tures. The same temperature coefficient was also found by previous 
authors for the time required for the development of the eggs of animals 
and incidentally also by us for the larval period of these flies; with this 
difference only, that in the latter case the coefficient is more regular. 
These experiments therefore show that the duration of life in the 
cases examined has a temperature coefficient of that order of magnitude 
which is characteristic for life phenomena and for chemical reactions in 
general. 
iLoeb, J., Arch, ges Physiol, 124, 411 (1908). 
2Metchniko£f, E., Ann. Inst. Pasteur, 29, 477, (1915). 
