A Fast‐Swimming “Mutant” in Stock 51 of <i>Paramecium aurelia</i>, Variety 4*

Abstract

SYNOPSIS. Animals arising spontaneously in a culture of Paramecium aurelia , variety 4, strain 51.8s, swam about three times as rapidly as normal 51.8s, 51.7s or 29.8 animals. When the 51‐fast animals were mixed with 51.8 or 29.8 paramecia, a random sampling of swimming rates showed a bimodal distribution. The faster rate of 51‐fast animals was maintained under such deleterious conditions as 48‐hour starvation. “Fastness” or “slowness” could not be selected for in vegetative clones. The 51‐fast paramecia would not mate with 51.7, 51.8 or 29.8 animals, although fission rate, serotype and general appearance indicated that 51‐fast probably arose from strain 51.8.