Studies on Reactions to Stimuli in Unicellular Organisms. Ii. - the Mechanism of the Motor Reactions of Paramecium?

A S pointed out in No. I. of these Studies,2 most of the reactions of Paramecium (as well as other Protozoa) are known only in their general features. The mechanism of the reactions,that is, the motions of the cilia by which they are brought about, has been determined for Paramecium only in Ludloff’s study3 of electrotaxis and my own of thigmotaxis. It is the purpose of the present paper to supply the lack thus indicated by giving a detailed account of the mechanism of the motor reactions of Paramecium. The far-reaching importance of an accurate knowledge of the exact mechanism of the reactions of Paramecium is apparent when we recall the sweeping conclusions that have been drawn from the results of studies on the reactions of this and other unicellular organisms. Theories of the mechanism of thermotaxis, geotaxis, and other reactions have been put forth, accompanied by deductions as to the remarkable sensitiveness of protoplasm to the various classes of reagents, and these theories have borne an important part in forming various prevalent conceptions in general physiology and in compara-