Note 6 — Chapter I

This difficulty is also felt by mechanistic writers like Child, who on page 12 of his recent book on Senescence and Rejuvenescence (Chicago, 1915) makes the following remarks: “These theories of Weismann do not account satisfactorily for the peculiarly constant course and character of development and morphogenesis. If we follow them to their logical conclusion, which their authors have not done, we find ourselves forced to assume the existence of some sort of controlling and co-ordinating principle outside the units themselves and superior to them. If the units constitute the physico­chemical basis of life, as their authors maintain, then this controlling principle, since it is an essential feature of life, must of necessity be something which is not physico­chemical in nature. In short these theories lead us in the final analysis to the same conclusion as that reached by the neovitalists. If we are not content to accept this conclusion we must reject the theories.” These last sentences do not exhaust all the possibilities, since the writer is trying to show in this book that the widest acceptance of the chromo­some theory of heredity is compatible with a consistent physico­chemical concep­tion of the organism as a whole.