The role of the cytoplasm in antigen determination in Paramecium aurelia

Abstract

Paramecium, because of its peculiar life cycle, is an unusually suitable organism for a study of the role of the cytoplasm in variation and development. During conjugation there is a reciprocal interchange of gamete nuclei, followed by fusion of ‘male’ and ‘female’ nuclei in each partner, but there is usually no significant passage of cytoplasm between the mates. After conjugation, therefore, each of the ex-conjugants contains identical sets of genes, but may differ cytoplasmically, if the cytoplasms of the conjugants had been different. Making use of this situation, paramecium workers, led by Dr T. M. Sonneborn, have studied the nuclear and cytoplasmic factors involved in the control of several different kinds of hereditary trait. I wish to stress here, however, that there is no overall uniformity amongst these systems. For example, the killer and antigen systems of paramecium are totally different. By contrast with the extraordinary regularity of the Mendelian system in different groups of organisms, cytoplasmic factors—in the very few cases where they have been thoroughly studied—are extremely diverse. Generalizing from one example to another is, therefore, unwise.