By back-crossing for twenty or more generations to the original paternal line, the genomes from three inbred lines of Drosophila melanogaster were introduced into cytoplasm of different origin. Two or four parallel lines were established from each cross. The back-crossing followed a protocol with a 14-or 28-day generation interval, respectively. Tests of the lines propagated with a 14-day interval (CF.) showed that the same genome introduced into cytoplasm from seven different strains resulted in two groups, which showed disparate effects on the frequencies of XXY and XO exceptionals and on fecundity. The parallel lines were inter se similar. Two sets with four parallel lines in each had sister lines propagated with a 28-day generation interval (CL). The CE lines and their CL sister lines differed.It is shown that cytoplasmic specificity may differ between strains and that this specificity is maintained for a great number of generations with very slight random variation. The disparity between CF and CL lines from the same original cross indicates an influence of the internal environment on cytoplasm in eggs formed in pupae and in adults, respectively, during the back-crossing.Comparisons between different genomes introduced into cytoplasm of common origin revealed different responses.The relation to the hybrid dysgenesis syndrome is discussed.
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