Aquatic Lite 
165 
ated with it. Abundant oxygen decreases 
its toxity, because blood has a greater 
affinity for oxygen than for carbon di- 
oxide, and the latter is crowded out of 
combination. On account of the fact that 
it is usually accompanied by lack of oxy- 
gen, putrescible muck bottom, etc., its 
presence in quantities greater than 6 to 7 
cc. per liter, if accompanied by a bottom 
entirely of such muck would indicate that 
found that fishes do not live well in alka- 
line water, but become sluggish and in- 
active. Neutrality is likewise toxic to 
some fresh-water fishes. They require 
a certain amount of acid. The optimum 
acidity for different species differs. ‘The 
optimum for the bluegill (Lepomis pal- 
lidus Mit.) is 1 to 3 cc. of carbon dioxide 
per liter and for crappies (Pomo-xis an- 
nularis Raf.) 4 to 6 cc. per liter. Wells 
NEN NNN SENNA NNN NNN 
Krefitius adspersus 
SSIS SASS SE 
Purple-striped Gudgeon 
) 
& 
. 
a 
4 
ae 
ae 
Photograph by H. E. Finckh 
REINS AS AS SE SSS SSS 
ENN NEN NEN NNN ENS NUNN ENN NANENENNEN NEN 
the water was unsuitable for trout, 
basses, sunfishes and crappies. 
One of the most important character- 
istics of a water is its acidity or alka- 
linity. Protoplasm must maintain essen- 
tial neutrality or it will die. It possesses 
a very effective physico-chemical mech- 
anism based upon the presence in excess 
of very weak acids (carbonic and phos- 
phoric) and alkalies in the form of car- 
bonates and phosphates. Since proto- 
plasm must remain nearly neutral, the 
acidity or alkalinity of the surrounding 
medium cannot be great. Thus Wells 
showed by using various other acids that 
the hydrogen ions are the important fac- 
tor. 
tain concentration of hydrogen ion. Neu- 
trality 1s avoided by fishes. In the ab- 
sence of acidity they select alkaline in 
preference to neutral water. Fishes and 
various crustaceans will live in distilled 
water if it is slightly acid, while it is 
rapidly fatal if alkaline. The toxity of 
much ordinary distilled water is due to 
colloidal copper or other metal from cool- 
ers, in suspension in it—FrEsSH WATER 
BroLocy. 
In other words fishes require a cer- 
