promptly begin to merge the one into the other till they twain become one flesh in very truth. Here is the most primitive form of marriage in Nature. And here, in this union, or fusion, of separate entities of Germ-plasm, we have the beginning of sex. Such unions are common among these primeval forms of life. In many cases this “marriage” takes place between two particles of Protoplasm of which one is rather larger than the other. In such case the smaller is regarded as male, the larger as female. Here we have the first sign of “sexual differentiation” or the evolution of “male” and “female” individuals. Some such union, some such process of “rejuvenation” by the importation of “fresh blood” seems to be imperative for the continuance of existence throughout the whole animal world, even though it may take place at rare intervals of time. Why should this be? Is this strange meeting and commingling a matter of chance, or is the one seeking the other possessed by a ravenous mate-hunger? As we ascend higher in the scale it becomes apparent that life has gathered force. That primitive speck of jelly, the Amœba, with which we started, gave but two signs of animation—the power of movement, and hunger. Whether these responses to internal stimuli can be called instinctive is open to argument. But there can be no question about the instinctive nature of the behaviour of these higher animals. After the instinct to feed the two most powerful are the desire for self-preservation—the avoidance of danger—and the desire to mate. These two are the dominating instincts throughout the rest of the animal world, not even excepting man himself. The tremendous power of “mate-hunger” has been overlooked by a strange confusion between cause and effect. Almost universally its sequel, the production of offspring, has been regarded as the dominant instinct in the higher animals. This view has no foundation in fact. “Desire” for the sake of the pleasure it affords, and not its consequences, is the only hold on life which any race possesses. And this is true both in the case of man himself and of the beasts that perish. Wherever this instinct becomes weak, or defective, extinction speedily and inevitably follows. This “Amorousness” is the motive power of “Courtship” wherever it is met with; manifesting itself in the eccentric, and often grotesque posturings, or in the loud and often musical cries which constitute the study of courtship. Intensity of desire is indispensable to survival.