At the beginning of the present century Heape (1900), describing the sexual season of mammals, pointed out that sheep in the British Isles are sexually active during only a portion of the year.

The course of pregnancy was followed in three groups of Peppin-strain Merino ewes. Group 1 of seven ewes, maintained on a high plane of nutrition, all lambed; the mean birth weight of lambs was 8 lb. 6 oz. The six ewes in group 2, kept on a low plane of nutrition, all lambed; the mean birth weight of their lambs was 1 lb. 9 oz. lower (P<0·01). The seven ewes in group 3 kept on a low plane of nutrition and subjected daily to temperatures of 112° F. dry bulb, 92° F. wet bulb, produced only four lambs; the mean birth weight was 4 lb. 6 oz. less than those from group 1, and 2 lb. 13 oz. less than those from group 2 (P < 0·001).Scale photographs of the lambs, and X-rays and measurements of their long bones, after dissection, showed that the lambs of group 3 were miniatures: their skeletons were much reduced in size, whereas low nutrition alone (group 2), caused little skeletal reduction.The mechanism of dwarfing is not clear. However, fore-cannon bone lengths and liver weights, considered in relation to lamb birth weights indicated that it was not a nutritional effect.This study was undertaken at the Physiology Department, University of Queensland. It is a pleasure to thank Prof. W. V. Macfarlane for the valuable facilities, and for his help and encouragement.

The possibility of defining quantitatively the carcasses of cattle has been investigated and a procedure evolved, based upon "conformation", "finish", and "quality", which are the features appraised by beef-carcass graders. A series of ratios has been used to define "conformation" with respect to shape rather than to dimensional attributes. For example, length, "meatiness", and compactness, which are attributes of a hind leg, are described by a ratio of which the numerator is the "circumference" measurement at an anatomically fixed point whereas the denominator is a defined length measurement. The trade term "finish" is covered by a percentage assessment of the distribution of subcutaneous fat over the carcass whereas thickness of fat is the mean of two measurements of depth made at points fixed anatomically. The proportion of fat to lean is stated by a ratio of which the numerator is a maximal measurement of the depth of lean meat a t a defined situation and the denominator is the mean depth of subcutaneous fat. Attributes of "quality" are colour of fat, firmness of fat, "marbling", and colour of lean meat. A series of five defined colours has been used to classify colour in a sample of subcutaneous fat rendered by heat. Firmness of fat has been related to a series of iodine numbers of greater or lesser magnitude: firm, medium, soft, and oily fats were found to be classifiable by the reaction of the rendered substance to slight manual pressure exerted through a blunt probe. The degree of marbling was determined from the size relation of a petrol-ether extract to a sample portion of the carcass taken at a defined situation. Colour of lean meat was classified by reference to a series of defined colours which were given distinctive numbers. Quantitative figures from observations may he recorded for examination by statistical methods or they may be transposed as diagrammatic presentations which may be related to trade standards or to market types for the purpose of judging carcass competitions. The procedure may also be used to provide data from which a "fleshing index" can be determined. Examples of all three possibilities are stated. The procedure has been tested on three series of animals, from which measurement errors for individual carcasses were calculated and found to be satisfactorily low. However, it has not yet been adequately tested for the comparison of between-group differences in carcasses, principally because no animals suitable for such a test are likely to become available until experimental conditioning is undertaken. The procedure is, therefore, presented tentatively.

The seasonal changes in coat character of a control group of four young Poll Shorthorn cattle have been studied and compared with those of a similar group in which the daily photoperiod was altered to simulate the synchronous duration of daily lighting of the opposite (northern) hemisphere. Heat tolerance tests were conducted periodically as the animals assumed different coat types. The results show that the full range of coat changes which characterize well-nourished cattle of the type used in this experiment may, irrespective of seasonal temperature, be reversed by artificially reversing the seasonal trend of daylight duration. This is presumptive evidence that the natural light environment is a major controlling factor in the normal pattern of seasonal coat change which cattle of European origin exhibit. Cattle with sleek, summer-type coats have shown decisive heat tolerance superiority over those with deep, winter-type coats under the conditions of this experiment. Clipping tests indicate that it is the heavy coat itself which lowers heat tolerance, not a particular internal condition (of metabolism, for example) with which heavy-coatedness might be associated.