1. The digestive organs and contents of twelve lambs, varying in age from 1 to 5 weeks, have been examined for their proteolytic enzyme activity at pH 1·8, 3·5 and 8·5.

2. Enzyme activity at 1·8 was present only in the abomasum and its contents.

3. All tissues and contents examined were active on haemoglobin at pH 3·5.

4. Small intestine contents and pancreas alone were active on azocasein at pH 8·5.

5. The majority of tissues and contents increased their proteolytic activity with increase in age. The abomasum wall, however, increased in activity up to 21 days and thereafter decreased, both at pH 1·8 and 3·5.

6. Milk-clotting action was measured on abomasum wall and contents. There was an absence of milk clots in the abomasum after 21 days, by which time rumen function had commenced.

An investigation of the estimation of the fertility of bulls' semen was carried out using the Impedance Bridge. A significant relationship between fertility and Impedance Change Frequency was confirmed, and this relationship extended to a within-bull significance.

1. Controlled self- and cross-pollinations were performed on field bean plants. It was found that while manipulation of the flower stimulated seed setting, both self- and cross-pollination were equally effective.

2. Estimations of pollen germination on artificial medium, to which had been added extracts of styles or ovaries from the same or a different plant, gave some slight evidence of a specific inhibition by ‘self’ extracts. No analogous effect was detected on pollen tube growth.

3. Experiments in which the style was cut at varying intervals after pollination detected no difference between self- and foreign pollen in rate of growth through the style. Pollen placed on stigmas of immature flowers began growth at once although the fertility achieved was less than when mature flowers were used.

4. The composition of seed from mixed self- and cross-pollination was examined. Early application of foreign pollen increased the proportion of crossfertilization but the results were similar in hybrids and inbreds.

5. Flower manipulation was more effective in stimulating seed setting than shaking the plants. Spraying with hormone solution was ineffective.

6. It was found that plants varied in their capacity to set seed without flower manipulation (autofertility). Hybrid plants were more autofertile than plants from inbred lines.

7. X-ray pictures of unopened flowers suggested that the pollen may be more abundant and less diffuse in hybrids than in inbreds.

8. The expression of autofertility was affected by many genetic factors.

9. Seed produced by open pollination of F1 hybrids contained a much higher proportion derived from self-pollination than did seed from inbred plants grown in the same plot. Possible explanations for this difference, and some consequences for the population genetics of the species, are discussed.

1. An experimental test of the effects of 15, 30 and 60 mg. of hexoestrol (ear implants) on growth (over a period of 95 to 98 days) has been carried out in Argentina, using 172 Hereford steers (all 4–5 years old).

2. On pasture where the growth rate was only about 0·4 kg. a day, the optimum dose was 30 mg., which gave an extra 0·14 kg. per day.

3. The carcasses from the 30 mg. group were significantly heavier by 8 kg., those from the 15 mg. group by 7 kg., but those from the 60 mg. group were only 3 kg. heavier than those from the control group.

4. It is suggested that both the poorer response and the lower optimum dose were due to the poorer pastures on which this experiment was carried out.

5. Evidence for the carcasses of the treated animals being significantly leaner than the controls was given by the 60 nag. group—the grading was poorer, the excess kidney fat was less, and the subcutaneous fat was thinner.

6. Carcass measurements showed differences in the treated groups, but these in general followed the differences in carcass weight.

7. Measurements of width of thigh and thorax provided evidence that the depth of carcass had been increased by hexoestrol.

8. The incidence of ‘tail raising’ had been increased from 10% in the control group, to 50% and more in the 15, 30 and 60 mg. groups. Carcasses from such animals had a slightly greater width at the thigh.

9. The existence of an optimum dose is not thought to be due to restlessness, as indicated by ‘tail raising’, but to a depressant action of hexoestrol on growth. In this connexion, data on the weights of the kidneys show that the 60 mg. dose decreases kidney weight (and implicitly the level of protein metabolism) to the value of the control.

10. Evidence was obtained of a rapid change in live weight when the steers were without food. During a single morning this was, on the average, about 13 kg. per animal, followed by a further 25 kg. during the subsequent 24 hr. (see Appendix II).

Maize stomata are shown to be markedly affected by severe drought lasting about a week or more, in that they do not recover their apparent pattern of normal behaviour after the water supply to the plant is restored, although the leaves regain their turgidity and seem normal. On the other hand, sorghum stomata recover well from severe drought lasting 14 days and their recovery follows fairly closely behind the restoration of turgidity to the leaves. It is suggested that this difference in ability of stomata to recover from severe drought in some measure accounts for the superiority of sorghum as a grain crop in dry regions.

Severe drought in maize is shown to be less damaging to the young plant than to the old, because the stomata of the unopened leaves behave normally when unfolded after the drought is broken.

1. Observations were made on the behaviour of young spring- and autumn-bom calves reared at pasture.

2. Bucket-fed calves rapidly learnt to graze, whereas single-suckled animals running with their dams made no serious attempt to graze until they were 6 weeks old.

3. The time spent in grazing was modified by the presence of hay and probably by that of concentrates, and it was influenced also by the quality and quantity of herbage on offer.