He thinks it difficult to believe that the wing of a bird "was
developed in any other way than by a comparatively sudden modification of a
marked and important kind;" and apparently he would extend the same view to
the wings of bats and pterodactyles. This conclusion, which implies great
breaks or discontinuity in the series, appears to me improbable in the
highest degree.
Everyone who believes in slow and gradual evolution, will of course admit
that specific changes may have been as abrupt and as great as any single
variation which we meet with under nature, or even under domestication.
But as species are more variable when domesticated or cultivated than under
their natural conditions, it is not probable that such great and abrupt
variations have often occurred under nature, as are known occasionally to
arise under domestication. Of these latter variations several may be
attributed to reversion; and the characters which thus reappear were, it is
probable, in many cases at first gained in a gradual manner. A still
greater number must be called monstrosities, such as six-fingered men,
porcupine men, Ancon sheep, Niata cattle, etc.; and as they are widely
different in character from natural species, they throw very little light
on our subject. Excluding such cases of abrupt variations, the few which
remain would at best constitute, if found in a state of nature, doubtful
species, closely related to their parental types.
Pages:
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390