50 THE CHICAGO ACADEMY OF SCIENCES. 
atmosphere. Undoubtedly much air was absorbed by this boiled water 
during the experiment, but even so, it may be assumed with a fair 
degree of certainty that the water in this dish was poorer in oxygen 
than the spring water. The snails were observed for one hour, during 
which time those in spring water came to the surface to breathe 20 
times, while those in the boiled water came up 44 times.” 
The results of these experiments show that when the Lymnzas 
are prevented from coming to the surface for atmospheric air they die. 
Mr. H. S. Colton’ has conducted a number of interesting experi- 
ments on Pseudosuccinea columella, along the lines of those conducted 
by Semper, Willem, Walter, etc. His conclusions are interesting and 
agree for the most part with those of Walter. Some of the more in- 
teresting points not recorded in the previous pages are as follows 
(see op. cit., p. 446-447) : 
“1. It was found that the presence of sand in the gizzard was 
necessary to enable the animal to assimilate plant tissue. 
“2. The accumulation of fecal matter, when washed and filtered 
had a beneficial effect on the growth of the animal; this is contrary to 
the result obtained by De Varigny. 
“3. Calcium salts in the water seem on the whole beneficial to 
growth, calcium sulphate particularly so. 
“4. Alternate Condition. Snails under unfavorable conditions 
when placed under favorable ones grow faster than if they were con- 
tinuously in favorable conditions. It would seem that the change 
from unfavorable to favorable conditions of life acts as a stimulant 
for growth. However, this does not always mean that it surpasses the 
control size. It rarely does that. 
“5. Not only does the environment affect growth, but it affects 
the number of eggs laid in a given time. This fact is very important, 
because it shows that the environment probably affects all the physi- 
ological processes and not one alone. 
“6. This study reveals the fact that confinement influences the 
growth of aquatic animals in three ways—through the amount of 
food, through the amount of oxygen, and through the accumulations 
of the waste products of metabolism. The phenomenon is not a simple 
one, and each factor plays its own part.” 
Dr. Howard N. Lyon, a Chicago physician, has raised Galba re- 
fiexa from the egg in a four-quart battery jar, under equal conditions 
of heat and light, the brood being from a single egg capsule. Fifteen 
1Proc. Phil. Acad., 1908, pp. 410-448. 
