ditions, gradually pushed back to earlier stages of ontogeny, so that what is the ultimate stage of one form is the penultimate of the next" (p. 277). To this argument, Hurst could muster only a feeble, slightly apologetic, and rhetorical reply.

Recapitulation would fall only when the two laws necessary to its operation—terminal addition and condensation—became untenable in theory. In the meantime, neither a catalog of exceptions, nor the assertion that undisputed facts fit another theory better, would budge it. Only when Mendelian genetics made terminal addition and condensation untenable in theory, could T. H. Morgan gain acceptance for his reincarnation of von Baer's position as " the repetition theory." Only then could Shumway sound his battle cry—" let us return to the law of von Baer" (1932, p. 98). Only then could Garstang proclaim in his gentler way: "Ontogeny is not a lengthening trail of dwarfed and outworn gerontic stages. Youth is perennially youth and not precocious age" (1922, p. 90).

Benign Neglect: Recapitulation and
the Rise of Experimental Embryology

The empirical critiques of the first thirty years had not shaken Haeckel's theory. In 1890, Marshall devoted his presidential address before the British Association to the biogenetic law, " which forms the basis of the science of Embryology, and which alone justifies the extraordinary attention this science has received" (1891, p. 827). And, in 1893, Bather praised a journal for daring to print Hurst's support of von Baer's principles against the biogenetic law: "Natural Science is to be congratulated on the publication of an article so opposed to current belief . . . for it has thereby shown that it will not burke views simply because they are unfashionable, but rather that it is ready to afford a free field to all genuine knights-errant who dare to smite the shields of authority."

By 1914, MacBride was lamenting: "In these days this law is regarded with disfavour by many zoologists, so that to rank oneself as a supporter of it is to be regarded as out-of-date. The newest theory is, however, not necessarily the truest" (p. 49). What had happened in the twenty years separating Bather and MacBride?

The Prior Assumptions of Recapitulation

As late nineteenth-century science became more mechanistic and experimental,18 the basic explanatory structure that nurtured the biogenetic law began to ring with a progressively more archaic sound.