RACIAL DIFFERENCES IN THE EARLY PHYSIOLOGICAL EFFECTS OF CONJUGATION IN PARAMECIUM AURELIA

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Abstract
(1) A comparison of 3 groups of ex-conjugants obtained at different times from the same clone. In all 3, the mean fission rate was the same as that of the parent clone, though in each group both the standard deviation and coefficient of variation of fission rate were greater than in the parent clone. (2) A comparison of 6 groups of ex-conjugants obtained at the same time from 6 clones. In standard deviation and coefficient of variation of fission rate and in percentage of mortality, the 6 groups fell into 3 significantly different grades. One group had a slightly higher mean fission rate ("rejuvenescence") than its parent clone; one group had the same mean as its parent clone; one group had a mean 50% lower than its parent clone ("depression"). In one clone, conjugation did not significantly increase variation in fission rate; in other clones conjugation greatly increased variation in fission rate. In some clones conjugation did not increase mortality, in others it greatly increased mortality. (3) Repeated simultaneous comparison of the effects of conjugation in 2 clones. In 4 comparisons, the same results were always obtained: one clone always produced groups of ex-conjugants with higher mean fission rate, lower coefficient of variation of fission rate, and lower mortality than the other clone. In the former clone, conjugation regularly left the mean fission rate unaltered, but in the latter the mean fission rate was always markedly decreased. The coefficient of variation of fission rate and the mortality rate were always increased less by conjugation in the former clone than in the latter. These 2 clones, differing so regularly in the effects of conjugation, were induced to conjugate with each other. The cross-bred groups of ex-conjugants differed from both parent clones and also from groups of inbred conjugants of either parent clone. Thus the effects of conjugation may differ characteristically in different clones of the same species. These differences in effect of conjugation depend upon differences in the constitutions of the conjugating individuals. The relation of these results to current theories of conjugation is pointed out.

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