This doctrine of the continuity of germ-plasm throws a fresh light on the nature of human relationships. It is evident that the son who resembles his father can not accurately be called a "chip off the old block." Rather, they are both chips off the same block; and aside from bringing about the fusion of two distinct strains of germ-plasm, father and mother are no more responsible for endowing the child with its characters except in the choice of mate, than is the child for "stamping his impress" on his parents. From another point of view, it has been said that father and son ought to be thought of as half-brothers by two different mothers, each being the product of the same strain of paternal germ-plasm, but not of the same strain of maternal germ-plasm. Biologically, the father or mother should not be thought of as the _producer_ of a child, but as the trustee of a stream of germ-plasm which produces a child whenever the proper conditions arise. Or as Sir Michael Foster put it, "The animal body is in reality a vehicle for ova or sperm; and after the life of the parent has become potentially renewed in the offspring, the body remains as a cast-off envelope whose future is but to die." Finally to quote the metaphor of J. Arthur Thomson, one may "think for a moment of a baker who has a very precious kind of leaven; he uses much of this in baking a large loaf; but he so arranges matters by a clever contrivance that part of the original leaven is always carried on unaltered, carefully preserved for the next baking. Nature is the baker, the loaf is the body, the leaven is the germ-plasm, and each baking is a generation." When the respective functions and relative importance, from a genetic point of view, of germ-plasm and body-plasm are understood, it must be fairly evident that the natural point of attack for any attempt at race betterment which aims to be fundamental rather than wholly superficial, must be the germ-plasm rather than the body-plasm. The failure to hold this point of view has been responsible for the disappointing results of much of the sociological theory of the last century, and for the fact that some of the work now carried on under the name of race betterment is producing results that are of little or no significance to true race betterment. On the other hand, it must be fairly evident, from the pains which Nature has taken to arrange for the transmission of the germ-plasm from generation to generation, that she would also protect it from injury with meticulous care. It seems hardly reasonable to suppose that a material of this sort should be exposed, in the higher animals at least, to all the vicissitudes of the environment, and to injury or change from the chance of outward circumstances.