Eight populations ofDrosophila melanogaster were raised to varying levels of inbreeding:F=0.000, 0.250, 0.375, 0.500, 0.672, 0.734, 0.785 and 0.908. Estimates of covariances between full sibs and between half sibs for bristle number and wing length were made in each of these populations. The estimates for bristle number showed a linear rise with increase inF values. Statistically, the rise was not significant. The estimate for wing length did not show any specific trend in relation to the level of inbreeding. The results are discussed in the light of theoretical expectations.

Neither mean chaeta number nor mean wing length was affected by inbreeding.

Variation due to dominant effects of genes for wing length was found in all the populations. Three populations also showed non-additive genetic variation for bristle number.

The phenotypic variance tended to increase with increase in the level of inbreeding up to F=.500 and beyond this, it tended to decline.