Page - 376 - in The Origin of Species

376 ORIGIN OF SPECIES succession of the productions of the land than with those of the sea. Thus, as it seems to me, the parallel, and, taken in a large sense, simultaneous, succession of the same forms of life throughout the world, accords well with the principle of new species having been formed by dominant species spreading widely and varying; the new species thus produced being themselves dominant, owing to their having had some ad- vantage over their already dominant parents, as well as over other species, and again spreading, varying, and producing new forms. The old forms which are beaten and which yield their places to the new and victorious forms, will gen- erally be allied in groups, from inheriting some inferiority in common; and therefore, as new and improved groups spread throughout the world, old groups disappear from the world; and the succession of forms everywhere tends to correspond both in their first appearance and final disappear- ance. There is one other remark connected with this subject worth making. I have given my reasons for believing that most of our great formations, rich in fossils, were deposited during periods of subsidence; and that blank intervals of vast duration, as far as fossils are concerned, occurred dur- ing the periods when the bed of the sea was either stationary or rising, and likewise when sediment was not thrown down quickly enough to embed and preserve organic remains. During these long and blank intervals I suppose that the in- habitants of each region underwent a considerable amount of modification and extinction, and that there was much migration from other parts of the world. As we have rea- son to believe that large areas are affected by the samemove- ment, it is probable that strictly contemporaneous formations have often been accumulated over very wide spaces in the same quarter of the world ; but we are very far from having any right to conclude that this has invariably been the case, and that large areas have invariably been affected by the same movements. When two formations have been deposited in two regions during nearly, but not exactly, the sarne period, we should find in both, from the causes explained in the foregoing paragraphs, the same general succession in