The younger generation of experimentalists extended their challenge. Speaking at the Marine Biological Laboratory in Woods Hole, E. B. Wilson asserted the birthright of a new movement:

[It is] a just ground of reproach to morphologists that their science should be burdened with such a mass of phylogenetic speculations and hypotheses, many of them mutually exclusive, in the absence of any well-defined standard of value by which to estimate their relative probability. The truth is that the search after suggestive working hypotheses in embryological morphology has too often led to a wild speculation unworthy of the name of science; and it would be small wonder if the modern student, especially after a training in the methods of more exact sciences, should regard the whole phylogenetic aspect of morphology as a kind of speculative pedantry unworthy of serious attention. There can be no doubt, I think, that this state of things is leading to a distaste for morphological investigation of the type represented, for instance, by Balfour and his school, while the brilliant discoveries of the cytologists and experimentalists . . . have set up a new tendency that gathers in force from day to day. (1894, pp. 103–104)

An anecdote cited by Oppenheimer (1967, pp. 74–75) illustrates the acrimony inspired by such assertions. In 1891, Hans Driesch sent to Haeckel a book in which he tried to explain the orientation of cleavage planes by mathematical formulae and physical principles: "He knew his book would not be looked upon with favor by Haeckel, but he sent him a copy, together with a letter asking whether development of the individual might not be considered from this new point of view. Neither the letter nor the book was acknowledged, but in due time Haeckel sent him an unwritten message, through a mutual friend, suggesting that Driesch take off some time in a mental hospital."

He did not (though his experimental colleagues might have made the same suggestion many years later after he converted to vitalism and shifted to philosophy). And Haeckel eventually retired to the empyrean, harmless height of elder statesman. What his empirical critics could not achieve by direct attack, his methodological opponents won by benign neglect.27 One can search through volumes of Roux's Archiv, scan the longest textbooks of experimental embryology, and not find a single reference to recapitulation.

Recapitulation and Substantive Issues in
Experimental Embryology: The New Preformationism

The first major controversy within experimental embryology so strongly recalled the attitudes of a previous debate that its names were reincarnated. The new epigeneticists, like Driesch, spoke of a " bar-