Abstract
The process of the transition from immaturity to maturity in the clonal development of Paramecium multimicronucleatum, syngen 2 was examined in detail. It was revealed that the three sex-traits, i.e., the abilities to undergo mating reaction, holdfast union and paroral union, were expressed sequentially with clonal age; first clones expressed none of the sex-traits (immature stage), secondly only the ability to undergo mating reaction (early transitional stage), then the ability to undergo holdfast union as well as mating reaction (late transitional stage), and then the ability to undergo paroral union as well as the abilities to undergo mating reaction and holdfast union (mature stage). It was also revealed that the intensity of the expression of each sex-trait increased with clonal age.
