ng
passage that he could maintain it only in a somewhat modified form. "It
is certain," he writes, "that if a given organ shows in the embryo of a
higher animal a given form, identical with that shown throughout life by
an animal belonging to a lower class, the embryo, in respect of this
portion of its economy, belongs to the class in question" (p. 535). The
embryo of a Vertebrate might at a certain stage of development, be
called a mollusc, if for instance, it had the heart of a mollusc.

He admits, too, that the highest animal of all does not pass through in
his development the entire animal series. But the embryo of man always
and necessarily passes through many animal stages, at least as regards
its single organs and organ-systems, and this is enough in Meckel's eyes
to justify the law of parallelism (p. 535).

In his excellent discussion of teratology Meckel points out how the idea
of parallelism throws light upon certain abnormalities which are found
to be normal in other (lower) forms (p. 556).[151]

We may refer to one other statement of the law of parallelism--by K. G.
Carus in his _Lehrbuch der vergleichenden Anatomie_ (Leipzig, 1834). The
standpoint is again that of _Naturphilosophie_. It is a general law of
Nature, Carus thinks, that the higher formations include the lower; thus
the animal includes the vegetable, for it possesses the "vegetative" as
well as the "animal" organs. So it is, too, by a rational necessity that
the development of a perfect animal repeats the series of antecedent
formations.

As we have said, the main credit for the enunciation of the law of
parallelism belongs to the German transcendental school; but the law
owes much also to Serres, who, with Meckel, worked out its implications.
It might for convenience, and in order to distinguish it from the laws
later enunciated by von Baer and Haeckel, be called the law of
Meckel-Serres.

Under the "theory of the repetition or multiplication of parts within
the organism" may be included, first, generalisations on the serial
homology of parts, and second, more or less confused attempts to
demonstrate that the whole organisation is repeated in certain of the
parts. The recognition of serial homologies constituted a real advance
in morphology; the "philosophical" idea of the repetition of the whole
in the parts led to many absurdities. It led Oken to assert that in the
head the whole trunk is repeated, that the upper jaw corresponds to the