If I understand this aright, the conclusion seems forced upon us that parental conduct is directly dependent on the action of the sexual appetite: that it may be modified, and in some cases profoundly changed, by any variation in this appetite’s strength and expression. This is of profound interest, and such a view, if established, might explain a great deal.[34] But can it be accepted? To say that such changes are due to the action of the “hormones,” or secretions of the sexual glands, does not help us very much. What we want to know is what induces the changes. There is much that cannot yet be explained. If I may venture to speculate on so difficult a question, it would seem that when the intensity of sex-hunger becomes for any reason stronger in the females than in the males, the result may be a diminishing of the instincts of motherhood. It is as if the egotistic desires of sex were in opposition to the racial duties. This would explain the female phalaropes, whose maternal instincts are completely atrophied. Does it not suggest also a possible explanation of some failures in human motherhood? This opens up questions that reach very far. I am tempted to wait to enlarge on the immense significance of these unnatural bird-mothers in the analogy their conduct bears to one of the most difficult cases of human motherhood—the strongly sexual woman who bears children but is quite unfit and without any desire to rear them. I shall have more to say in the later part of my inquiry about such women, who are driven by passion to be mothers without having any instinct for motherhood. But now a return must be made to the birds’ nurseries. It is a matter of common knowledge that birds display a marvellous solicitude for the welfare of the young, and their family life presents a beautiful and high standard of conduct.[35] There are very few examples of birds who are bad fathers. Often the male rivals the female in love for the young; he is in constant attendance in the vicinity of the nest; he guards, feeds, and sings to the female, and often shares with her the duty of incubation. The cock ostrich, for example, watches by night over the hole in which the eggs have been buried, and the hen takes this duty by day. The screamer birds, again, work in shifts of two or three hours each. When they bred in the London Zoological Gardens, it was noticed that the cock-bird acted as timekeeper, and at the end of a watch used to come and push the female off the nest.[36] These examples are delightful. It would seem almost that the males, when infected with paternal passion, were more ardent and regular in the performance of nursery duties than the mother.