206 



ERNEST WARREN. 



and pi'essure with the rate at which the solution acts on 

 Daphuia, i.e. the rate at which the molecules of salt strike 

 the animal. 



2. The Rate of Killing as a Function of Tempera- 

 ture, the Strength of the Salt Solution being 

 kept Constant. 



Some observations were made on the effect of temperature 

 on the rate of killing. TG per cent, and 2 per cent, solutions 

 were employed. The results are given in the following 

 table : 



Table III. 



It is obvious from the accompanying diagram (Fig. 2) 

 that the observations may fairly be represented by the inter- 

 polated curves. The points found on the curves^'are some- 

 what too few, butj as we shall see later on, the blanks could 

 not now be filled up ; for unless the fresh Daphnia employed 

 were exactly in the same physiological condition as those 

 used for the rest of the curve they would not be comparable. 

 Since the points that were found are sufiicient to show the 

 general effect of temperature it was not thought to be neces- 

 sary to do the experiments afresh. 



The point at which heat-rigor occurred was 38-25° C. 

 [= 101° F.]. This was determined by slowly (i. e. taking 



