animals must, as they add organs in their own development, pass through the permanent stages of those lower on the scale: "The whole animal kingdom is none other than the representation of the several activities or organs of Man; naught else than Man disintegrated" (1847, p. 19).

During its development the animal passes through all stages of the animal kingdom. The foetus is a representation of all animal classes in time. At first it is a simple vesicle, stomach, or vitellus, as in the Infusoria. Then the vesicle is doubled through the albumen and shell, and obtains an intestine, as in the Corals.

It obtains a vascular system in the vitelline vessels, or absorbents, as in the Acalephae.

With the blood-system, liver, and ovarium, the embryo enters the class of bi- valved Mollusca.

With the muscular heart, the testicle, and the penis, into the class of Snails. With the venous and arteriose hearts, and the urinary apparatus, into the class of Cephalopods or Cuttle-fish.

With the absorption of the integument, into the class of Worms. With the formation of branchial fissures, into the class Crustacea. With the germination or budding forth of limbs, into the class of Insects. With the appearance of the osseous system, into the class of Fishes. With the evolution of muscles, into the class of Reptiles. With the ingress of respiration through the lungs, into the class of Birds. The foetus, when born, is actually like them, edentulous.* (1847, pp. 491–492)

J. F. Meckel's Sober Statement
of the Same Principles

It is often assumed that to be a Naturphilosoph one had to engage in the kind of mystical and cosmic pronouncement that Oken favored (Mayr, 1965). But in fact, many scientists who shared Oken's philosophy wrote in a very dry and controlled fashion; allegiance to a school

* It is important to understand what Oken means by these statements, lest he be dismissed as a madman. The human embryo at the time it forms branchial fissures is surely not a crustacean. Oken is not concerned with the external appearance of crabs, their size, their shape, the arrangement of their parts. The crab merely represents or symbolizes an ideal step in universal progression by addition of organs: the respiratory organ in its branchial form (all else about a crab is irrelevant). When the human fetus develops gill slits, it has reached the stage of ontogeny that crabs symbolize in the historical sequence of adults (all else, again, being irrelevant). C. G. Carus, an influential Naturphilosoph and supporter of Oken, wrote: "Each degree of development of a superior animal constantly recalls a determined form of an inferior organism; but between the two there is no complete identity, but only a resemblance of fundamental nature or essence" (1835, 2: 438).