Page:The Depths of the Sea - Wyville - 1873.djvu/41

] Ernst Haeckel, Dr. Fritz Müller, and others of their enthusiastic disciples and commentators. I do not think that I am speaking too strongly when I say that there is now scarcely a single competent general naturalist who is not prepared to accept some form of the doctrine of evolution.

There is, no doubt, very great difficulty in the minds of many of us in conceiving that, commencing from the simplest living being, the present state of things in the organic world has been produced solely by the combined action of 'atavism,' the tendency of offspring to resemble their parents closely; and 'variation,' the tendency of offspring to differ individually from their parents within very narrow limits: and many are inclined to believe that some other law than the 'survival of the fittest' must regulate the existing marvellous system of extreme and yet harmonious modification. Still it must be admitted that variation is a vera causa, capable, within a limited period, under favourable circumstances, of converting one species into what, according to our present ideas, we should be forced to recognize as a different species. And such being the case, it is, perhaps, conceivable that during the lapse of a period of time—still infinitely shorter than eternity—variation may have produced the entire result.