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 Lymnaeas 

 are prevented from coming to the surface for atmospheric air they die. 



Mr. H. S. Colton 1 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 faecal 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- 

 flexa 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 



J Proc. Phil. Acad., 1908, pp. 410-448. 



