240 STUDIES IN GENERAL PHYSIOLOGY 
its specific gravity increased. He seems to have overlooked 
the osmotic effects. The following indicates Schmanke- 
witsch’s (physiologically untenable) conception of the effect of 
the air dissolved in the salt water: “If the salt water is not 
diluted very gradually, the specimens of Artemia salina die 
of exhaustion, attributable probably to the increase of oxida- 
tions due to the greater amount of air in the more diluted 
sea-water.” In this case we probably have to do with the 
fact that in the rapid dilution of the salt water the proto- 
plasm of the cells of Artemia is suddenly flooded with water;' 
it is an effect similar to that brought about by rapidly thawing 
out frozen organs. I will not deny, of course, that the 
decrease in the amount of oxygen dissolved in a salt solution 
can also inhibit growth when it exceeds a certain limit. This 
is shown very clearly by the following experiments. 
XI. THE NECESSITY OF OXYGEN IN REGENERATION 
When sea-water was boiled, and Tubularian stems intro- 
duced into it after it had cooled, no regeneration of polyps 
occurred; if, however, I shook the boiled water for a time 
thoroughly with air, regeneration followed. Water there- 
fore must contain a certain minimal concentration of oxygen 
in order to render regeneration possible. 
But it can also be shown that the end of a Tubularian 
which is to regenerate must be surrounded by water contain- 
ing a definite amount of oxygen, and that it is not sufficient 
to have merely the remaining portions of the Tubularia 
taking up oxygen. The bottom of an aquarium was covered 
with fine sand. I set glass tubes 5cem. long and 3-4mm. in 
diameter vertically in the sand. The upper end of the tube 
(Fig. 61) was drawn to a point a, which was just suf- 
ficiently fine to allow the stem of a Tubularian to pass 
1 Recent experiments which I have made point to the possibility that the rapid 
diffusion of salts from the animal when it is brought into more dilute solutions 
is, in some animals, the cause of death, [1903] 
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