ed with their relative
time of occurrence during phylogeny. Thus the notochord, the brain, the
eyes, the heart, appear earlier in the ontogenetic than in the
phylogenetic series, while, on the other hand, the septum of the
auricles appears in the development of the higher Vertebrates before the
ventricular septum, which is undoubtedly a reversal of the phylogenetic
order.

Cases of heterotopy, or of organs being developed in a position or a
germ-layer other than that in which they originally arose in phylogeny,
are not so easy to find. According to Haeckel, the origin of the
generative products in the mesoderm is a heterotopic phenomenon, for he
considers that they must have originated phylogenetically in one of the
two primary layers, ectoderm or endoderm.

It is worthy of note that the help of comparative anatomy is admittedly
required in deciding what processes are palingenetic and what
cenogenetic (p. 412).

Haeckel's morphological notions, and particularly his biogenetic law,
excited a good deal of adverse criticism from men like His, Claus,
Salensky, Semper and Goette. Nor was his principal work, the _General
Morphology_, received with much favour. Nevertheless, since he did
express, though in a crude, dogmatic and extreme manner, the main
hypotheses upon which evolutionary morphology is founded, his historical
importance is considerable. He cannot perhaps be regarded as typical of
the morphologists of his time--he was too trenchantly materialistic, too
much the populariser of a crude and commonplace philosophy of Nature. In
point of concrete achievement in the field of pure research he fell
notably behind many of his contemporaries.

His friend, Carl Gegenbaur, who gained a great and well-deserved
reputation by his masterly studies on vertebrate morphology,[380] was a
sounder man, and probably exercised a wider and certainly a more
wholesome influence upon the younger generation of professional
morphologists than the more brilliant Haeckel. It is true that in his
famous _Grundzuege der vergleichenden Anatomie_, the second edition of
which, published in 1870, soon came to be regarded as the classical
text-book of evolutionary morphology, Gegenbaur enunciated very much the
same general principles as Haeckel, and referred to the _Generelle
Morphologie_ as the chief and fundamental work on animal morphology. But
in Gegenbaur's pages the Haeckelian doctrines are modified and subdued
by the strong commonsense and