he
German transcendental school for the law of the parallelism between the
stages of individual development and the stages of the scale of beings,
and the theory of the repetition or multiplication of parts within the
individual. The vertebral theory of the skull is a particular
application of the second of these generalisations.

The law of parallelism[141] seems to have been expressed first by
Kielmeyer (1793),[142] who gave to it a physiological form, saying that
the human embryo shows at first a purely vegetative life, then becomes
like the lower animals, which move but have no sensation, and finally
reaches the level of the animals that both feel and move.

The idea was next taught by Autenrieth in 1797.[143]

Oken (1779-1851) in his early tract _Die Zeugung_ (1805), and in his
_Lehrbuch der Naturphilosophie_ (1809-11) elaborated the thought, and
taught that every animal in its development passes through the classes
immediately below it. "During its development the animal passes through
all stages of the animal kingdom. The foetus is a representation of all
animal classes in time."[144] The Insect, for example, is at first Worm,
next Crab, then a perfect volant animal with limbs, a Fly (_ibid._, p.
542).

As Nature is "the representation of the individual activities of the
spirit," so the animal kingdom is the representation of the activities
or organs of man. The animal kingdom is therefore "a dismemberment of
the highest animal, _i.e._, of Man" (p. 494). Now "animals are gradually
perfected, entirely like the single animal body, by adding organ unto
organ"--the way of evolution is the way of development. Hence "animals
are only the persistent foetal stages or conditions of Man," who is the
microcosm, and contains within himself all the animal kingdom.

Oken was himself a careful student of embryology; von Baer[145] speaks of
his work (published in Oken and Kieser, _Beitraege zur vergleichenden
Zoologie, Anatomie und Physiologie_, 2 pts., 1806-7) as forming the
turning-point in our understanding of the mammalian ovum. He had
accordingly actually observed a resemblance in certain details of
structure between the human foetus and the lower animals; but the
peculiar form which the law took in his hands was a consequence of his
hazy philosophy. He saw the relation of teratological to foetal
structure, for he affirmed that "malformations are only persistent
foetal conditions" (p. 492).

The idea of comparing the