The male stickleback, as many of you may know, builds a wonderful nest, in which, when finished, he invites his chosen mate to lay her eggs. As soon as these precious treasures have been entrusted to his care, he makes himself their sole guardian, forcing currents of fresh water through the nest by the violent fanning motion of his breast-fins, and driving away all that come near. Strangely enough, he has to exercise the greatest care to keep out his mate, who would eat every single egg if she could but get the chance!