The same interpretation must obtain where the numerical values of the sexes is reversed. Failure to appreciate this accounts for one of the many futile suggestions made for the suppression of the rabbit plague in Australia, which was that large hauls of these pests should be made by netting, and that the females should be slain and the males released. This, it was held, would lead to the speedy reduction of the latter, which would kill one another in their fights for the remaining females. The plan was impracticable, but the suggestion demonstrated the prevalent belief as to the attitude of the male in this respect. Had it been well founded, surely polyandrous species, whether of birds or beasts, would never have existed; for, by the reduction of the males, monogamy would speedily have been restored. How, then, are we to explain polyandry? How are we to explain the fact, as it seems to be the fact, that the excess of males has brought about such a complete reversal in behaviour—the males, instead of the females, requiring the aphrodisiac? The solution of this problem probably lies with the physiologist. We now know that the problem of sex does not rest merely in the complete development of the primary sexual organs; we know that fertile unions do not depend merely on the act of pairing, but on the functional activity of those ancillary glands already referred to. And it may well be that some change in the character of the secretions has not only altered the numerical values of the sexes, but reversed the normal rôle of coloration and behaviour. That is to say, neither polygamy nor polyandry among the lower animals, at any rate, has been brought about or is maintained by the excessive death-rate due to combats for possession of mates, but must be explained as demonstrating inherent changes in the germ-plasm, disturbing the relative proportions of the sexes and correlated with a profound transformation, not only in the behaviour of the sexes during the period of reproductive activity, but also in their physical characteristics. The action of the primary sexual glands and of the ancillary glands has, then, to be allowed for in all attempts to interpret behaviour in sexual matters. No less so must this be the case in regard to the development of coloration and other forms of ornament, and the genesis of weapons of offence. But at present we are, in this direction, dealing with an unknown quantity. The recognition of this, however, should not deter us from attempting to solve the riddle of sex from the phenomena which have so far been surveyed.