n, were it not that old
transition-stages can be called forth by particular temperatures, and
we know other butterflies, as for instance our Garden Whites, in which
the differences between the two generations are not nearly so marked;
indeed, they are so little apparent that they are scarcely likely to
be noticed except by experts. Thus here again there are small initial
steps, some of which, indeed, must be regarded as adaptations, such as
the green-sprinkled or lightly tinted under-surface which gives them a
deceptive resemblance to parsley or to Cardamine leaves.

Even if saltatory variations do occur, we cannot assume that these
_have ever led to forms which are capable of survival under the
conditions of wild life_. Experience has shown that in plants which
have suddenly varied the power of persistence is diminished.
Korschinsky attributes to them weaknesses of organisation in general;
"they bloom late, ripen few of their seeds, and show great
sensitiveness to cold." These are not the characters which make for
success in the struggle for existence.

We must briefly refer here to the views--much discussed in the last
decade--of H. de Vries, who believes that the roots of transformation
must be sought for in _saltatory variations arising from internal
causes_, and distinguishes such _mutations_, as he has called them,
from ordinary individual variations, in that they breed true, that is,
with strict in-breeding they are handed on pure to the next
generation. I have elsewhere endeavoured to point out the weaknesses
of this theory,[33] and I am the less inclined to return to it here
that it now appears[34] that the far-reaching conclusions drawn by de
Vries from his observations on the Evening Primrose, _Oenothera
lamarckiana_, rest upon a very insecure foundation. The plant from
which de Vries saw numerous "species"--his "mutations"--arise was not,
as he assumed, a _wild species_ that had been introduced to Europe
from America, but was probably a hybrid form which was first
discovered in the Jardin des Plantes in Paris, and which does not
appear to exist anywhere in America as a wild species.

This gives a severe shock to the "Mutation theory," for the other
_actually wild_ species with which de Vries experimented showed no
"mutations" but yielded only negative results.

Thus we come to the conclusion that Darwin[35] was right in regarding
transformations as taking place by minute steps, which, if useful, are
aug