480 RECAPITULATION. 



tween each and some extinct and supplanted form. Even 

 on a wide area, which has during a long period remained 

 continuous, and of which the climatic and other conditions 

 of life change insensibly in proceeding from a district oc- 

 cupied by one species into another district occupied by a 

 closely allied species, we have no just right to expect often 

 to find intermediate varieties in the intermediate zones. For 

 we have reason to believe that only a few species of a genus 

 ever undergo change; the other species becoming utterly 

 extinct and leaving no modified progeny. Of the species 

 which do change, only a few within the same country 

 change at the same time; and all modifications are slowly 

 eifected. I have also shown that the intermediate varieties 

 which probably at first existed in the intermediate zones, 

 would be liable to be supplanted by the allied forms on 

 either hand; for the latter, from existing in greater num- 

 bers, would generally be modified and improved at a 

 quicker rate than the intermediate varieties, which existed 

 in lesser numbers; so that the intermediate varieties would, 

 in the long run, be supplanted and exterminated. 



On this doctrine of the extermination of an infinitude of 

 connecting links, between the living and extinct inhabi- 

 tants of the world, and at each successive period be- 

 tween the extinct and still older species, why is not 

 every geological formation charged with such links? Why 

 does not every collection of fossil remains afford plain evi- 

 dence of the gradation and mutation of the forms of life? 

 Although geological research has undoubtedly revealed the 

 former existence of many links, bringing numerous forms 

 of life much closer together, it does not yield the infinitely 

 many fine gradations between past and present species re- 

 quired on the theory, and this is the most obvious of the 

 many objections which may be urged against it. Why, 

 again, do whole groups of allied species appear, though 

 this appearance is often false, to have come in suddenly on 

 the successive geological stages? Although we now know 

 that organic beings appeared on this globe, at a period in- 

 calculably remote, long before the lowest bed of the Cam- 

 brian system was deposited, why do we not find beneath 

 this system great piles of strata stored with the remains of 

 the progenitors of the Cambrian fossils? For on the 

 theory, such strata must somewhere have been deposited at 



