eludes some examples still cited today. He writes, for example, that the mammalian heart is first simple and tubular, as in insects; it then acquires a single chamber like that of crustaceans; later, when it possesses an auricle, ventricle, and aortic bulb, it represents the heart of fishes; when the auricle becomes divided, it adopts the reptilian form. At the end of his list, Meckel then appends this simple, concluding paragraph: "These few pages will suffice to prove that the analogy between the human embryo and the lower animals is unmistakable [unverkennbar], and that the completion of this parallel by exact and careful investigations of the human embryo and that of other animals . . . is one of the most desirable objectives of a rational anatomy, physiology, and zoology."

Serres and the French Transcendentalists

Naturphilosophie was not the only biological translation of the new, developmental view of nature. The French transcendental morphologists, under the leadership of Etienne Geoffrey Saint-Hilaire, shared a set of assumptions with their German colleagues, including the belief that all animals are built upon a single, structural plan; the idea of a chain of being; and a belief in recapitulation (Russell, 1916).

Geoffrey himself, though he gave the matter no particular attention, supported recapitulation. The development of this doctrine was left to his "chief follower" (Russell, 1916, p. 79), the medical anatomist Etienne Serres. Serres championed recapitulation in his monographs on the comparative anatomy of the vertebrate brain (1824–1826) and in a series of articles collectively titled "Recherches d'anatomie transcendante," published in the Annales des sciences naturelles during the 1820s and 1830s. As late as 1860, long after Geoffrey's time had passed, Serres wrote a thousand-page paean to his mentor, upholding Geoffrey's doctrines in scarcely modified form. In this work of his old age, Serres recalls the delight of his first demonstration of recapitulation forty years before.

I did not know how to express the feeling of admiration that I felt for the grandeur of the creation in general, and for that of man in particular, when I saw that, at a first stage [of ontogeny], the human brain resembled that of a fish; that at a second stage, it resembled that of reptiles; at a third, that of birds; and at a fourth, that of mammals, in order finally to elevate itself to that sublime organization that dominates all nature.(1860, pp. 398-399)

Geoffrey and his school took as their guiding belief the notion that all animals share a single plan of construction. The greatest challenge to this idea, so effectively exploited by Cuvier in his famous debate