(1) The ratio of the total lactation yield to the maximum yield, divided by the mean ratio (in the particular district) for the month of calving in which the lactation commenced, has been selected to represent the shape of each individual cow's lactation curve, and has been called the shape figure (S.F.).

(2) The variation of individual S.F.'s was found to be less than that of all cows taken together—i.e. the shape of the curve, though largely determined by environmental factors, is due partly to a genetic characteristic of the cow.

(3) The S.F.'s of 1st calvers are high (about 11 per cent, above those of subsequent lactations); i.e. heifers give a small maximum relative to their total yield.

(4) No significant relation was found between the length of the dry period preceding calving, and the ratio of the total to the maximum yield in the subsequent lactation.

(5) S.F.'s rise markedly and definitely as we pass from low to moderate, and from moderate to high, yielders; i.e. in good milkers the maximum is lower relative to the total yield than in bad milkers. Though there is variation from herd to herd (due probably to the system of management), this rise was shown between bad and good cows within the same herd, and seems to be a definite genetic character.