An analogous explanation has been given by Mr. Wallace, of the equally
complex case, of certain Malayan butterflies regularly appearing under two
or even three distinct female forms; and by Fritz Muller, of certain
Brazilian crustaceans likewise appearing under two widely distinct male
forms. But this subject need not here be discussed.
I have now explained how, I believe, the wonderful fact of two distinctly
defined castes of sterile workers existing in the same nest, both widely
different from each other and from their parents, has originated. We can
see how useful their production may have been to a social community of
ants, on the same principle that the division of labour is useful to
civilised man. Ants, however, work by inherited instincts and by inherited
organs or tools, while man works by acquired knowledge and manufactured
instruments. But I must confess, that, with all my faith in natural
selection, I should never have anticipated that this principle could have
been efficient in so high a degree, had not the case of these neuter
insects led me to this conclusion. I have, therefore, discussed this case,
at some little but wholly insufficient length, in order to show the power
of natural selection, and likewise because this is by far the most serious
special difficulty which my theory has encountered. The case, also, is
very interesting, as it proves that with animals, as with plants, any
amount of modification may be effected by the accumulation of numerous,
slight, spontaneous variations, which are in any way profitable, without
exercise or habit having been brought into play.
Pages:
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446