4TT
And indeed we find it very difficult to understand the
utility of some of the modifications which take place.
What advantage can it be, for example, to the insects
of a particular district to be coloured blue ? And yet,—
“ In a forest of Southern Brazil, Dr. Seitz found a perfectly circum
scribed region in which the insects were almost entirely blue ; a few
miles away from this locality the insects were red, yellow—any colour
but blue ; but in the particular locality blue was so characteristic
a tint that, out of twenty butterflies, ten were entirely blue, and the
remaining ten partially blue. Nor was blue found to be confined to
the Lepidoptera—the flies and hemiptera were also largely blue.”—
(Beddard. Animal Coloration, ft. 46.)
We cannot exactly see what advantage could accrue
to a tree from the adoption of a fastigate or pyramidal
growth, and yet the hotter parts of India modify some
trees in this way.
“Dr. Falconer informs me that he has seen the English Ribston
pippin apple, a Himalayan oak, Prunus and Pyrus, all assume in the
hotter parts of India a fastigate or pyramidal habit ; and this fact is
the more interesting, as a Chinese tropical species of Pyrus naturally
has this habit of growth.”—(The Variation, vol. ii., ft. 277.)
But it would be an immense mistake to infer that, because
transforming influences are not limited by the principle
of utility and can therefore put forth unuseful variations,
all the variations which occur through that agency alone
are not useful.
We have seen that transforming influences go on in
association with the output of individual differences. Now
it is quite clear that the absence of identity which dis
tinguishes one individual from another is useful, as those
will readily admit who have had to live with twins between
whom it was impossible to distinguish. We cannot doubt
that it is well that the shepherd should be able to dis
tinguish each individual sheep which he tends, and that the