test_, p. 40.]

[Footnote 207: _The Natural Conditions of Existence as they Affect
Animal Life._ London, 1883.]

[Footnote 208: In Dr. Weismann's essay on "Heredity," already referred
to, he considers it not improbable that changes in organisms produced by
climatic influences may be inherited, because, as these changes do not
affect the external parts of an organism only, but often, as in the case
of warmth or moisture permeate the whole structure, they may possibly
modify the germ-plasm itself, and thus induce variations in the next
generation. In this way, he thinks, may possibly be explained the
climatic varieties of certain butterflies, and some other changes which
seem to be effected by change of climate in a few generations.]

[Footnote 209: This brief indication of Professor Geddes's views is
taken from the article "Variation and Selection" in the _Encyclopedia
Britannica_, and a paper "On the Nature and Causes of Variation in
Plants" in _Trans. and Proc. of the Edinburgh Botanical Society_, 1886;
and is, for the most part, expressed in his own words.]

[Footnote 210: Placostylis bovinus, 31/2 inches long; Paryphanta Busbyi, 3
in. diam.; P. Hochstetteri, 23/4 in. diam.]

[Footnote 211: The general arguments and objections here set forth will
apply with equal force to Professor G. Henslow's theory of the origin of
the various forms and structures of flowers as due to "the responsive
actions of the protoplasm in consequence of the irritations set up by
the weights, pressures, thrusts, tensions, etc., of the insect visitors"
(_The Origin of Floral Structures through Insect and other Agencies_, p.
340). On the assumption that acquired characters are inherited, such
irritations may have had something to do with the initiation of
variations and with the production of certain details of structure, but
they are clearly incompetent to have brought about the more important
structural and functional modifications of flowers. Such are, the
various adjustments of length and position of the stamens to bring the
pollen to the insect and from the insect to the stigma; the various
motions of stamens and styles at the right time and the right direction;
the physiological adjustments bringing about fertility or sterility in
heterostyled plants; the traps, springs, and complex movements of
various parts of orchids; and innumerable other remarkable phenomena.

For the explanation of these we have no resource but variation and
s