I. Haeckel and His Opponents

The followers of the doctrine of violent transformations believed that the development of the earth had been accomplished in successive periods, definitely distinguished from one another. At the end of such a period there occurred a catastrophe. Everything living was destroyed, and its remains preserved in an earth-stratum. On the top of what had been destroyed there arose a completely new world, which must be created afresh. In the place of this doctrine of catastrophes, Lyell set up the view that the crust of the earth has been gradually moulded in the course of very long periods of time, by the same processes which still in our time are going on every day on the earth's surface. It has been the action of the rivers carrying mud away from one spot and depositing it on another; the work of the glaciers, which grind away rocks and stones, forward blocks of stone, and analogous processes, which, in their steady, slow working have given to the earth's surface its present configuration. This view necessarily draws after it the further conclusion that the present-day forms of plants and animals also have gradually developed themselves out of those whose remains are preserved for us in fossils. Now, it results from the processes of artificial breeding that one form can really transform itself into another. There remains only the question, by what means are those conditions for this transformation, which the breeder brings about by artificial means, created in Nature itself?