So the sex-instinct and its associated emotion, at first simply one among a number of separate and scarcely-correlated instincts, has in man become the basis for numerous new mental functions. It can enter into the composition of various emotions, though its character is often disguised and its presence often undetected. It contributes to some of the most exalted states of mind which we can experience. The sexual relationship, which in lower animals involves neither contact nor even propinquity, but simply simultaneous discharge of reproductive cells, and in most animals is a purely temporary affair, is very different in man. Even in those birds and non-human mammals in which the sexes remain associated for long periods or permanently, the different departments of life are more in water-tight compartments, the psychical activity is subordinate to the physiological: in man the physiological side, though of course still basic and necessary, is more--and can be much more--subordinate to the psychological, and all parts of the mental life interpenetrate to a much greater extent; so that the sex-instinct may become transformed by a psychological process roughly analogous to the transformation of physical energy, and reappear in altered guise in various other activities of mind. If we look at the matter broadly, we see that man is in a period of evolutionary transition as regards sex. We found previously that the greatest change connected with sex which has been made in the evolution of higher animals was the change by which there was evolved a brain and mind with associated sense-organs in which accurate perception of objects at a distance could occur, a mechanism which really dominated the working of the organism as a whole, and in which memory and emotion seemed to play an important part. Once this happened, the sex-instinct could be linked up with general emotional reactions and connected with external objects capable of inducing emotion. What was the result? That in every group possessing such a type of mind, epigamic characters of a beautiful or striking or bizarre nature were evolved. This first linking-up of sex with mind produced, eventually, a large proportion of the beauty of the organic world. It coloured and adorned not only many a bird, but even newts and fish and spiders; it helped elicit song and music from mere sounds and noises; it moulded our own bodies, coloured our lips and eyes, and everywhere helped in adding grace to mere serviceableness; it saw to it that, as St. Paul puts it, “even our uncomely parts have an abundant comeliness.” But, as we have just pointed out, its connection with the mind’s higher centres was in all pre-human forms still temporary, under the control of cyclical physiological changes, and the mind as a whole was still constructed in compartments, so that different instincts and different experiences did not necessarily or even usually come in contact with each other.