Puberty is defined as that stage of individual development characterised by the ability to elaborate functional gametes and by the physical ability to and the desire to play the appropriate rôle in mating. Maturity is defined as that stage of individual development characterised by the exhibition of the maximum fertility ratio and by the ability to produce viable offspring and to rear them.

It is shown that the age at attainment of puberty varies with different stock and with different conditions of husbandry, and that there can be no generally applicable standard. Each worker must standardise his own stock and his own environment.

There are considerable individual differences in the age at maturity, and these are referable to dissimilarities in genetic constitution and to differences in husbandry. In this experiment two groups of animals were involved, coloured and albino. The albinos reached puberty much earlier, showed a longer duration of the cornified stage before mating, a higher proportion of matings at first œstrus, a greater proportion of pregnancies following mating at first œstrus, and a slightly longer interval between first and second œstrus.