128 SUMMARY OF CHAPTEES. [Chap. XL 



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 generally become more 

 specialised ; and this may account for the common 

 belief held by so many palaeontologists, that organisa- 

 tion on the whole has progressed. Extinct and ancient 

 animals resemble to a certain extent the embryos of 

 the more recent animals belonging 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 palaeontology 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 



