Data for body length, depth, width, fore cannon length, fold score and mutton score were collected on two groups of Peppin Merino ewe lambs. The experimental animals comprised 284 ewe lambs born in the spring of 1951 (group ‘A’) and 273 born in the autumn of 1952 (group ‘W’) at the Trangie Agricultural Experiment Station of the New South Wales Department of Agriculture.

The estimates for heritability calculated by the method of intra-sire correlation for body depth, length, width, fore cannon length, fold score and mutton score are: 0.00, 0.00, 0.08, 0.16, 0.28 and 0.28 respectively in group ‘W’ and 0.29, 0.10, 0.48, 0.30, 0.79 and 0.10 in group ‘A’ and 0.01, 0.00, 0.27, 0.24, 0.46 and 0.13 in the combined groups (A & W). Estimate for fold score calculated by sire-offspring regression for both the groups is 0.34.

Covariances between full sibs and between half sibs were estimated for bristle number and wing length in different samples ofDrosophila melanogaster bred to varying levels of inbreeding. The estimates for bristle number increased linearly with increase inF values, but for wing length the trend appeared curvilinear with concavity towards the axis representingF values.

Mean chaeta number was not affected by the level of inbreeding, although there was an apparent trend in the reduction of wing length. Inbreeding depression measured by the number of flies which survived in each line was very apparent.

Non-additive genetic variance was found to be unimportant in these data.

The phenotypic variance, on the average, tended to decrease slightly with increase in inbreeding.

Data on wing length, bristle number and egg count were collected on two groups of full-sibs ofDrosophila ananassae, separated and raised at temperatures of 20° and 25°C from larval to adult stage. The flies raised at 20°C had longer wings and fewer bristles than those raised at 25°C. The number of eggs laid was also reduced at 20°C.

If the effect of change of temperature from 25° to 20°C on the level of production is considered, it is more marked on the high level groups of egg count and bristle number and low level group of wing length.

Analyses of data showed significant differences between temperatures for all the three characters. The differences between genotypes were significant for bristle number and wing length only. The genotype-temperature interactions were significant for all the three characters except for the bristle number in the female.

Genotype-temperature interactions have been expressed as intra-class correlations to determine their relative importance. It was concluded that these interactions were more important for egg count and wing length and relatively less important for bristle number.

Biometric data on bristle numbers for two segments and wing length of 936 femaleDrosophila melanogaster derived from a wild stock are presented. Heritabilities were about 0.4. The genetic correlation between the two bristle numbers was +.91, the environmental correlation insignificant. The genetic correlations between wing length and the bristle numbers were +39 and +.17, the environmental correlations again insignificant.

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.

Data on body length, chest girth, height and weight at birth of 404 Marwari lambs from 19 different sire-families were analysed. There was a significant phenotypic correlation between any two characters. All the environmental correlations except the one between body length and chest girth were smaller than the corresponding phenotypic correlations. The genetic correlation between body length and width was fairly low but all other correlations were very high, Heritability estimates for body length, height, chest girth and birth weight were 0.06, 0.42, 0.23 and 0.20, respectively.

On the basis of concentration of potassium in the blood, sheep can be classified into two distinct groups—high (HK) and low (LK). The two types have been observed to occur in all the seven indigenous breeds whereas only one type (LK) was noticed, in exotic breeds. There are distinct breed differences in the proportion of these types and concentration of potassium. The blood types are controlled by a single locus, KL being dominant over KH. There is evidence that KL is partially dominant. Exotic LK sheep are homozygous whereas indigenous LK are both heteroygous and homozygous. Natural selection is not operating against one of the types.

There were no significant differences between LK and HK in their water intake.