terised chiefly by
the catch-words "polyphyletic descent," "labile and stable equilibrium,"
and so on, crop up together or separately in the writings of various
evolutionists belonging to the opposition wing. They are usually
associated with a denial of the theory of natural selection, and with
theories of "Orthogenesis," "Heterogenesis," and "Epigenesis."

We shall discuss them later when we are considering the factors in
evolution. But we must first take notice of a work in which the theories
opposed to Darwinian orthodoxy have been most decisively and aggressively
set forth. As far back as 1892 O. Hamann, then a lecturer on zoology in
Goettingen, gathered these together and brought them into the field,
against Haeckel in particular, in his book "Entwicklungslehre und
Darwinismus."(27)

Hamann's main theme is that Darwinism overlooks the fact that "there
cannot have been an origin of higher types from types already finished."
For this "unfortunate and unsupported assumption" there are no proofs in
embryology, palaeontology, or anatomy. He adopts and expands the arguments
and anti-Haeckelian deliverances of His in embryology, of Snell and Heer
in palaeontology, of Koelliker and von Baer in their special interpretation
of evolution, of Snell particularly as regards the descent of man. It is
impossible to derive Metazoa from Protozoa in their present finished state
of evolution; even the Amoeba is so exactly adapted in organisation and
functional activity to the conditions of its existence that it is a
"finished" type. It is only by a stretch of fancy that fishes can be
derived from worms, or higher vertebrates from fishes. One of his
favourite arguments--and it is a weighty one, though neglected by the
orthodox Darwinians--is that living substance is capable, under similar
stimuli, of developing spontaneously and afresh, at quite different points
and in different groups, similar organs, such as spots sensitive to light,
accumulations of pigment, eye-spots, lenses, complete eyes, and similarly
with the notochord, the excretory organs, and the like. Therefore homology
of organs is no proof of their hereditary affiliation.(28) They rather
illustrate "iterative evolution."

Another favourite argument is the fact of "Paedogenesis." Certain animals,
such as _Amphioxus lanceolatus_, _Peripatus_, and certain Medusae, are very
frequently brought forward as examples of persistent primitive stages and
"transitional connecting li