376 ORIGIN OF SPECIES 



succession of the productions of the land than with those of 



the sea. j 



Thus, as it seems to me, the parallel, and, taken in a large I 



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 same move- 

 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 



