But
whenever the changed conditions are permanent, or are such that
individual adaptation cannot meet the requirements, then Natural
Selection rapidly brings about a permanent adaptation which is
inherited. In plants these two forms of adaptation are well marked and
easily tested, and we shall soon have a large body of evidence upon it.
In the higher animals I imagine that individual adaptation is small in
amount, as indicated by the fact that even slight varieties often breed
true.
In Lepidoptera we have the two forms of colour-adaptability clearly
shown. Many species are, in all their stages, permanently adapted to
their environment. Others have a certain power of individual adaptation,
as of the pupae to their surroundings. If this last adaptation were
strictly inherited it would be positively injurious, since the progeny
would thereby lose the power of individual adaptability, and thus we
should have light pupae on dark surroundings, and vice versa. Each kind
of adaptation has its own sphere, and it is essential that the one
should be non-inheritable, the other heritable. The whole thing seems to
me quite harmonious and "as it should be."
Thiselton-Dyer tells me that H. Spencer is dreadfully disturbed on the
question. He fears that acquired characters may not be inherited, in
which case the foundation of his whole philosophy is undermined!--Yours
very truly,
ALFRED R.
Pages:
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79