nd
orders, may not be the expression of the common conditions to which that
particular patch of nebulous fog, which may have been constituted by
their atoms, and of which they may be, in the strictest sense, the
descendants, was subjected?

It will be obvious from what has preceded, that we do not agree with
Professor Kolliker in thinking the objections which he brings forward
so weighty as to be fatal to Darwin's view. But even if the case were
otherwise, we should be unable to accept the "Theory of Heterogeneous
Generation" which is offered as a substitute. That theory is thus
stated:--

"The fundamental conception of this hypothesis is, that, under the
influence of a general law of development, the germs of organisms
produce others different from themselves. This might happen (1) by
the fecundated ova passing, in the course of their development, under
particular circumstances, into higher forms; (2) by the primitive and
later organisms producing other organisms without fecundation, out of
germs or eggs (Parthenogenesis)."

In favour of this hypothesis, Professor Kolliker adduces the well-known
facts of Agamogenesis, or "alternate generation"; the extreme
dissimilarity of the males and females of many animals; and of the
males, females, and neuters of those insects which live in colonies:
and he defines its relations to the Darwinian theory as follows:--"It
is obvious that my hypothesis is apparently very similar to Darwin's,
inasmuch as I also consider that the various forms of animals have
proceeded directly from one another. My hypothesis of the creation of
organisms by heterogeneous generation, however, is distinguished very
essentially from Darwin's by the entire absence of the principle of
useful variations and their natural selection: and my fundamental
conception is this, that a great plan of development lies at the
foundation of the origin of the whole organic world, impelling the
simpler forms to more and more complex developments. How this law
operates, what influences determine the development of the eggs and
germs, and impel them to assume constantly new forms, I naturally cannot
pretend to say; but I can at least adduce the great analogy of the
alternation of generations. If a 'Bipinnaria', a 'Brachialaria', a
'Pluteus', is competent to produce the Echinoderm, which is so widely
different from it; if a hydroid polype can produce the higher Medusa;
if the vermiform Trematode 'nurse' can develop within