pitulation requires if its occurrence be general), then condensation cannot be caused by natural selection because accelerated adult features often have no function in juvenile descendants. It must then be the result of some principle of inheritance. Not only does this principle work independently of natural selection (thereby compromising the general importance of Darwin's postulate), but it is also completely unknown:

Newly acquired characters undergo, as a whole, backward transference, by which means they are to a certain extent displaced from the final ontogenetic stage by characters which appear later. This must be a purely mechanical process, depending on that innate law of growth, the action of which we may observe without being able to explain fully. (1881, p. 280)

Yet, through a glass darkly, Weismann glimpsed the direction of the coming solution. The laws of heredity must first be established: "If we could see the determinants, and recognize directly their arrangement in the germ-plasm and their importance in ontogeny, we should doubtless understand many of the phenomena of ontogeny and their relation to phylogeny which must otherwise remain a riddle" (1904, p. 189).

The determinants were soon elucidated as Mendelian genes; but Weismann's idea of universal recapitulation did not survive. He knew that no proper test could be made in the absence of a theory of inheritance; he could not know that the coming theory would invalidate his own conviction. We will return to the fate of recapitulation in Chapter 6, following a discussion in Chapter 5 of the remarkable influence that recapitulation exerted in fields as diverse as politics and primary education.

Appendix: The Evolutionary Translation
of von Baer's Laws

In devoting most of this chapter to the mechanisms of recapitulation, I may have given the false impression that von Baer's alternative was nearly eclipsed or that Darwin was alone in his support of it. To be sure, von Baer's notion fared poorly among professional biologists in the late nineteenth century, only to be resurrected in our own. Yet it was adopted by two prominent evolutionists, neither in the main stream of professional science—Robert Chambers (author of the anomymous Vestiges of the Natural History of Creation) and Herbert Spencer. As the central theme of Spencer's cosmic defense of Victorian society, it became one of the most influential scientific ideas of the nineteenth century. Moreover, Ospovat (1974) has recently shown that von Baer's principle of increasing differentiation supplied the