structures, with
an elaborate vascular system, a pollen-chamber, and often a
much-differentiated testa. In the present day such seeds exist only in a
few Gymnosperms which retain their ancient characters--in all the higher
Spermophytes the structure is very much simplified, and this holds good
even in the Coniferae, where there is no countervailing complication of
ovary and stigma.

Reduction, in fact, is not always, or even generally, the same thing as
degeneration. Simplification of parts is one of the most usual means of
advance for the organism as a whole. A large proportion of the higher
plants are microphyllous in comparison with the highly megaphyllous
fern-like forms from which they appear to have been derived.

Darwin treated the general question of advance in organisation with much
caution, saying: "The geological record... does not extend far enough
back, to show with unmistakeable clearness that within the known history
of the world organisation has largely advanced." ("Origin of Species",
page 308.) Further on (Ibid. page 309.) he gives two standards by which
advance may be measured: "We ought not solely to compare the highest
members of a class at any two periods... but we ought to compare all the
members, high and low, at the two periods." Judged by either standard
the Horsetails and Club Mosses of the Carboniferous were higher than
those of our own day, and the same is true of the Mesozoic Cycads. There
is a general advance in the succession of classes, but not within each
class.

Darwin's argument that "the inhabitants of the world at each successive
period in its history have beaten their predecessors in the race for
life, and are, in so far, higher in the scale" ("Origin of Species",
page 315.) is unanswerable, but we must remember that "higher in the
scale" only means "better adapted to the existing conditions." Darwin
points out (Ibid. page 279.) that species have remained unchanged for
long periods, probably longer than the periods of modification, and only
underwent change when the conditions of their life were altered. Higher
organisation, judged by the test of success, is thus purely relative to
the changing conditions, a fact of which we have a striking illustration
in the sudden incoming of the Angiosperms with all their wonderful
floral adaptations to fertilisation by the higher families of Insects.

II. PHYLOGENY.

The question of phylogeny is really inseparable from that of the truth