: 
; 
4 
, 
385 
It seems abundantly demonstrated that various fresh-water fishes 
will live in pH 9.0. This is shown by the work of Miss Hall on white- 
fish and by the observation of Garrey (716) in connection with the St. 
Louis city water. The resistance of forms other than fish, especially ~ 
stagnant water bottom-forms may be great. Stickney (’22) found 
that a dragon-fly nymph, Libellula pulchella, lived in very high H ion 
concentrations. It tolerated pH 1.0 for 12 hours or more. Miss Hall 
found toads’ eggs very resistant as compared with those of whitefish. 
REACTIONS OF FisH TO DIFFERENCES IN HyproGcEN Ion 
CONCENTRATIONS 
A large series of experiments was conducted by the author* with 
ten species of fish and a number of types of water; aerated well-water, 
boiled water, distilled water, rain-water, etc. The results are given in 
Table V and in Figure 1. In nearly all cases the fishes reacted definitely 
to differences. With any given temperature, salt content, etc., they 
usually behaved consistently, and with any one set of conditions could 
be depended on to select a given hydrogen ion concentration; but as 
conditions were varied and the number of readings increased the results 
_ varied and were as represented in Table V and Figure 1. The selections 
tend to fall in two or three places, which with a larger number of read- 
ings would probably be reduced to one maximum. Each species will 
be seen to have a definite range which differs from every other species— 
as shown by the polygons. All figures run higher with the Na,CO,. 
An average of approximately twelve experiments were run with each 
species (the exact number is given in Table V). Fishes accustomed to 
live in clear open waters, especially the minnows, select the lower hydrogen 
ion concentrations. It is evident from the range of concentrations se- 
lected by them that all these species might be found in the same small 
stream during non-critical periods. The order in which the species 
arrange themselves corresponds to the frequency of their occurrence in 
the bodies of water mentioned (Fig. 1). 
The range selected by each species is rather wide, though with a few 
exceptions the fishes show unmistakable evidences of reacting. Some 
of the reasons for the broken character of the curves, irregularities, wide 
range selected, and variation from time to time are as follows: (1) differ- 
ences in salt content of the water, both experimental differences and 
those due to differences in aeration in storage reservoirs; (2) difference 
in steepness of the gradient—a difference of 6.5 to 8.2 would not be en- 
countered in so short a distance in nature. 
The following additional reactions have been estimated from pub- 
lished graphs and by calculations by one of the equations of Greenfield 
and Baker (’20), which are presented on page .388. 
* For methods see Bul. Ill. State Lab. Nat. Hist., Vol. 11 (Art. VI), page 293. 
