FEEDING REACTIONS IN THE CILIATE,<i>DILEPTUS GIGAS</i>, WITH SPECIAL REFERENCE TO THE FUNCTION OF TRICHOCYSTS

Abstract

1. Dileptus gigas normally feeds on living organisms, but under certain conditions it ingests inanimate particles. 2. It discriminates between living organisms and inanimate substances, ingesting the former in large amounts, while the latter are only sparingly ingested. 3. Dileptus selects from among different kinds of organisms, eating some with great readiness, while others are rarely ingested. 4. It captures its prey by means of trichocysts which either paralyze the prey, e.g., Euglena, or bring about cytolysis of all or part of the protoplasm of the prey, e.g., Colpidium and Stentor. 5. The trichocysts are probably of a liquid nature, highly toxic, with specific cytolytic properties. 6. The trichocysts of Dileptus are used for the purpose of capturing food. 7. Selection of food in Dileptus depends on two factors: (a) The physiological state of the organism itself, which appears to determine whether a substance shall be ingested in large or small amounts, and (b) the chemical properties of its trichocysts, which determine in large measure whether any living organism can or can not be successfully captured. 8. Specialized structures as, for example, the trichocysts of Paramecium and the lorica of Euplotes, serve as protection against the attacks of Dileptus.