The significance of the varied behaviour of birds—more especially of the males—during the period of reproductive activity must now be more minutely analysed. But before this analysis can be profitably begun, it will be necessary to recall the fact that there are several cases known wherein the rôle of the sexes is largely reversed. Herein the females do the “courting,” and fight one another as rivals for the males; while the males perform the duties of incubation and brooding, and feeding the young. This is really very remarkable, and demands more attention than it has yet received. What factors have brought about this curious reversal? In any search for an explanation it must be borne in mind that in all such cases polyandry is the rule, and in all such cases the female is larger and more vividly coloured than the male. Here, then, we have exactly the opposite to what obtains in cases of polygamy. What is the reason for this preponderance of males? Why is it that when the males are in excess of the females the latter should be the more brilliantly coloured and the more amorous? These questions at present are unanswerable. When polygamy obtains it seems always to be assumed that it is explained by the excessive pugnacity of the males, which, after fierce contests for the mastery, take forcible possession of as many females as may be captured and held in durance; the same argument seems never to have been applied when polyandry obtains. There can be no doubt but that it applies in neither case. When polygamy obtains, as we have already pointed out, the females are not seized and captured by the males, they are not victims of a lecherous lord. On the contrary, they seek the males, and the intensity of the desire to satisfy their natural cravings extinguishes any feeling of jealousy.