As we have just said, Love is concerned with growth and evolution. It is—though as yet hardly acknowledged in that connection—a root-factor of ordinary human growth; for in so far as it is a hunger of the individual, the satisfaction of that hunger is necessary for individual growth—necessary (in its various forms) for physical, mental and spiritual nourishment, for health, mental energy, large affectional capacity, and so forth. And it is—though this too is not sufficiently acknowledged—a root-factor of the Evolution process. For in so far as it represents and gives rise to the union of two beings in a new form, it plainly represents a step in Evolution, and plainly suggests that the direction of that step will somehow depend upon the character and quality of the love concerned. Thus the importance, the necessity, of the study of the art of love is forced on our attention. It has to be no longer a subterranean, unrecognized, and even rather disreputable cult, but an openly acknowledged and honorable department of human life, leading in its due time to broad and commonsense instructions and initiations for the young. * * * * * Casting a glance back at the love-affairs of the Protozoa, as briefly described in the preceding chapter, there certainly seems to be a kind of naive charm about them. The simple and wholehearted way in which on occasions they fuse with one another, losing or merging completely their own separate individualities in the process; or again part from each other after having exchanged essences in a kind of affectionate cannibalism; the obvious and unconcealed relation between love and hunger; the first beginnings of generation; and the matter-of-fact manner in which one person, when he finds it convenient, divides in half and becomes two persons, and after a time perhaps divides again and becomes four persons, and again and again until he is many thousands or millions—and yet it is impossible to decide (and he himself probably is not quite clear) as to whether he is still one person or different persons—all this cannot fail to excite our admiration and respect, nor to give us, also, considerable food for thought.