And further, of the genesis of this Human Soul: "With the growth of the higher centres, the capacities of action become so various and indeterminate that definite direction is not given to them until after birth." By the increase of cerebral surface, infancy, which is the period of plasticity, is prolonged, Man becomes teachable, and though inherited tendencies and aptitudes still form the foundations of character, yet the career of the individual is no longer wholly predetermined by the careers of its ancestors, but individual experience comes to count as an enormous factor in modifying the career of mankind from generation to generation. The psychical development of humanity since its earlier stages has been largely due to the reaction of individuals upon one another in those various relations which we characterize as social. Foreshadowings of social relations occur in the animal world. Rudimentary moral sentiments are also clearly discernible in the highest members of various mammalian orders and in all but the lowest members of our own order. But in respect of definiteness and permanence, the relations between animals in a state of gregariousness fall far short of the relations between individuals in the rudest human society. The primordial unit of human society is the family, the establishment of which was made necessary and took place through the lengthening of infancy. When childhood had come to extend over a period of ten or a dozen years, a period which would have been doubled where several children were born in succession to the same parents, the relationships between father and mother, brothers and sisters, must have become firmly knit; thus the family came into existence, and the way was opened for the growth of sympathies and ethical feelings. The rudimentary form of the ethical feelings was that of the transient affection of a female bird or mammal for its young. First given a definite direction through the genesis of the primitive human family, the development of altruism has yet scarcely kept pace with the general development of intelligence; the advance of civilized man in justice and kindness has been less marked than his advance in quick intelligence. But the creative energy which has been thus at work through the bygone eternity is not going to become quiescent to-morrow; the psychical development of man is destined to go on in the future as it has in the past. And from the "Origin of Man," when thoroughly comprehended, we may catch some glimpses of his destiny.