Chap. XI.] PRECEDING AND PRESENT CHAPTERS. 316 



The inhabitants of the world at each successive period in its 

 history have beaten their predecessors in the race for life, and 

 are, in so far, higher in the scale, and their structure has gene- 

 rally become more specialised ; and this may account for the com- 

 mon belief held by so many paleontologists, that organisation on 

 the whole has progressed. Extinct and ancient animals resemble 

 to a certain extent the embryos of the more recent animals belong- 

 ing to the same classes, and this wonderful fact receives a simple 

 explanation according to our views. The succession of the same 

 types of structure within the same areas during the later geological 

 periods ceases to be mysterious, and is intelligible on the principle 

 of inheritance. 



If then the geological record be as imperfect as many believe, and 

 it may at least be asserted that the. record cannot be proved to be 

 much more perfect, the main objections to the theory of natural 

 selection are greatly diminished or disappear. On the other hand, 

 all the chief laws of palajontology plainly proclaim, as it seems to 

 me, that species have been produced by ordinary generation : old 

 forms having been supplanted by new and improved forms of life, 

 the products of Variation and the Survival of the Fittest. 



