MELDOLA
_Parkstone, Dorset. October 12, 1896._
My dear Meldola,--I got Weismann's "Germinal Selection" two or three
months back and read it very carefully, and on the whole I admire it
very much, and think it does complete the work of ordinary variation and
selection. Of course it is a pure hypothesis, and can never perhaps be
directly proved, but it seems to me a reasonable one, and it enables us
to understand two groups of facts which I have never been able to work
out satisfactorily by the old method. These two facts are: (1) the
total, or almost total, disappearance of many useless organs, and (2)
the continuous development of secondary sexual characters beyond any
conceivable utility, and, apparently, till checked by inutility. It
explains both these. Disuse alone, as I and many others have always
argued, cannot do the first, but can only cause _regression to the
mean_, with perhaps some further regression from economy of material.
As to the second, I have always felt the difficulty of accounting for
the enormous development of the peacock's train, the bird of paradise
plumes, the long wattle of the bell bird, the enormous tail-feathers of
the Guatemalan trogon, of some humming-birds, etc. etc. etc. The
beginnings of all these I can explain as recognition marks, and this
explains also their distinctive character in allied species, but it does
not explain their growing on and on far beyond what is needful for
recognition, and apparently till limited by absolute hurtfulness.
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