Among low forms—inferior to the human organism—the germs of new individuals are produced in immense numbers, the larger part of the parental substance being sometimes transformed into these germs. Birth here may be immediately followed by the death of the parent organism, and an immense mortality of the young may take place—consequent on defenceless exposure, insufficient food and other untoward conditions. “Of a million minute ova left uncared for, the majority are destroyed before they are hatched, so that very few have considerable amounts of individual life.” (Ibid. p. 622.) Throughout the course of evolution the natural order in moving from higher to higher types is a gradual decrease of this condition, viz. the sacrifice of individual life to the life of the species, and at the same time an increase of compensating pleasures allied with the reproductive function. When illustrating this natural order, Herbert Spencer points to the methods among fishes and amphibians contrasted with those among birds and mammals. The spawn of the former when safely deposited is generally left to its fate.[3] There is physical cost to adults with apparently no accompanying gratifications. Birds and mammals, however, carefully rear and tend their offspring. “The activities of parenthood are sources of agreeable emotions, just as are the activities which achieve self-sustentation.” Footnote 3: There are exceptions to the rule, as in the case of the male stickleback. Passing from the less intelligent vertebrates which produce many young at short intervals and abandon them at an early age, to the more intelligent higher vertebrates which produce few young at longer intervals and aid them for longer periods, this principle clearly emerges—“While the rate of juvenile mortality is diminished, there results both a lessened physical cost of maintaining the species and an augmented satisfaction of the affections.” (_Principles of Sociology_, vol. i. p. 628.) There is no reversal of this genetic order of nature in the epoch of conscious evolution. The processes are different, because man possesses developed intellect, aided by scientific knowledge and invention as a new and skilled ally in the struggle to maintain his species at less and less cost of individual life and happiness; but the general forward movement takes precisely the same course. With the highest evolved type of man this sacrifice of individual life to the species is reduced to a minimum, while the interests of species are conserved in a painless, a wholly superior manner. And, further, the entire range of domestic feelings—parental, filial, fraternal and intimately social, become extended and increasingly capable of bestowing enduring pleasure. The ultimate goal is easy maintenance of species, without—to any unpleasurable extent—subordinating single members of species to that end.