Abstract
Spontaneous crossover values from males of D. ananassae showed great individual variation. From such a variable population two-way selection was started selecting randomly twenty heterozygous males from testcross progeny of a male with highest crossing over and from one with lowest values. Similar selection was continued for 15 generations. Wide variations in generation means were observed. The high line exceeds the low line significantly in mean crossover frequency. The difference in the two lines was established although the progressive increase was not significant. Since the difference in the two lines was established the effect of selection is genetic.
