381 
Hydrogen ion concentration is expressed as pH—the logarithm of 
NG the reciprocal of the normality of free hydrogen ions. The pH scale 
a and relative amounts of free hydrogen ions are as follows: 
ig >) 
4 = A 
; fc 5 F 
a Oo =i = 
7 <q 2 < 
aa a t#t[U oO 
Mw Drees 2 ee wt Gl aie Oo Oh. LO 1. 12) 038% 14 
L ame er a leon (elo bead [hk aft] 
Es SS LSet era SU tr a ee rie te Vi re 
‘* Sono Onto. Jour rs} Nae a 
' oe ey ied SSS SS 
ie (= = i — eee | Se et Se See 
f Som S fort = ei 
ve o o = —) o i=) 
ta art o So 
i. x = 
E 
The range to be expected in Illinois waters is about 8.5 to 6.7 for 
most streams and lakes not contaminated. Streams receiving mine seep- 
( age may have much higher hydrogen ion concentrations and still support 
- certain species of fish. 
Tue INFLUENCE OF Hyprocen Ion CONCENTRATION ON FERTILIZATION, 
DEVELOPMENT, GROWTH, AND SURVIVAL IN WATER DEFICIENT 
IN DIssoLVED OXYGEN 
1. Fertilization of fish eggs—Miss Hall found that when oxygen 
is 4 c.c. per liter fertilization of the eggs of the whitefish takes place 
equally well in acid, neutral, and alkaliiie waters. When oxygen is 
lower (2.9 c.c. per liter) pH 6.2-6.6 is more favorable to fertilization 
than 7.0-8.4. This relation is quite inexplicably the reverse of what 
would be expected by comparison with other relations to oxygen. 
2. Development.—Miss Hall showed that in the toad and whitefish 
the early cleavage and gastrulation period is most sensitive to hydrogen 
ion concentration and low oxygen. She further showed that early death 
or retarded development occurred in both toad and whitefish embryos 
with pH 6.2 and O, about 1 c. c. per liter. In the case of the whitefish, 
still lower oxygens gave little difference correlated with pH. The experi- 
ments with sufficient oxygen indicate that pH 7.0 is near the maximum 
H ion concentration which permits best development. Even so high a 
concentration is probably not common on fish breeding-grounds in Illinois 
waters. Higher concentrations, to pH 6.2, show interference with de- 
velopment, hatching, or length of life. That acid interferes with de- 
velopment was demonstrated by Loeb in 1898, and this having been 
found generally true, of marine animals at least, the demonstration has 
become a class experiment with marine forms. 
3. Survival.—The influence of hydrogen ion concentration on the 
survival of fishes in low-oxygen water is shown in Tables I-IV. 
