vored races the right to dominate others; the irrational mysticism that had always stood in strange communion with his brave words about objective science—all contributed to the rise of Nazism. The Monist League that he had founded and led, though it included a wing of pacifists and leftists, made a comfortable transition to active support for Hitler.
Our narrow subject impinges upon these wider implications of Haeckel's beliefs, for Haeckel buttressed many of his political claims by references to recapitulation. He refutes the innate superiority of aristocrats, for example, by stating that all men are lowly creatures during their early development:
Even in our day, in many civilized countries, the idea of hereditary grades of rank goes so far that, for example, the aristocracy imagine themselves to be of a nature totally different from that of ordinary citizens . . . What are these nobles to think . . . when they learn that all human embryos, those of nobles as well as commoners, are scarcely distinguishable from the tailed embryos of dogs and other mammals during the first two months of development. (1905, p. 337)
The Mechanism of Recapitulation
"Phylogenesis," Haeckel wrote in Anthropogenie, "is the mechanical cause of ontogenesis" ("Die Phylogenese ist die mechanische Ursache der Ontogenese"— 1874, p. 5). "The connection between them is not of an external or superficial, but of a profound, intrinsic, and causal nature" (1874, p. 6); the two processes stand "in dem engsten mechanischen Causalnexus" (1866, 2: xix). These strong words, reflecting the aggressively mechanistic attitude of Haeckel's time, have often been ridiculed in our more cynical age.5 Yet, although Haeckel was almost addicted to obfuscation by using fashionable words in meaningless contexts, it is important to recognize that when he said "phylogeny is the mechanical cause of ontogeny" he really meant it. The mechanism of recapitulation, as Haeckel envisaged it, provided just such a causal link.
The vitalistic forces of Naturphilosophie could be invoked no longer as the cause of recapitulation. Instead, Haeckel declared his allegiance with physiology in seeking the new path of mechanistic causation:
Phylogenesis . . . is a physiological process, which, like all other physiological functions of organisms, is determined with absolute necessity by mechanical causes. These causes are motions of the atoms and molecules that comprise organic material . . . Phylogenesis is therefore neither the foreordained, purposeful result of an intelligent creator, nor the product of any sort of