On the Reaction of Daphnia magna (Straus) to certain Changes in its Environment

For some years I have been engaged in breeding Daphnia magna (Straus), for the purpose of obtaining data which would be of value in testing the current theories, of heredity. The investigation has led me to a series of experiments on the action of common salt, and on the effect of a confined volume of water on this animal. Some of the results seem to present certain features of considerable interest and of wide biological significance; they illustrate how closely the organism is knit to its external conditions of life.