■Chap. XL State of Development. 307 



On the theory of descent, the full meaning of the fossil remains 

 from closely consecutive formations being closely related, though 

 ranked as distinct species, is obvious. As the accumulation of each 

 formation has often been interrupted, and as long blank intervals 

 have intervened between successive formations, we ought not to 

 expect to find, as I attempted to show in the last chapter, in any 

 one or in any two formations, all the intermediate varieties between 

 the species which appeared at the commencement and close of these 

 periods : but we ought to find after intervals, very long as measured 

 by years, but only moderately long as measured geologically, 

 closely allied forms, or, as they have been called by some authors, 

 representative species ; and these assuredly we do find. We find, 

 in short, such evidence of the slow and scarcely sensible mutations 

 of specific forms, as we have the right to expect. 



On the State of Development of Ancient compared with Living 



Forms. 



We have seen in the fourth chapter that the degree of differentia- 

 tion and specialisation of the parts in organic beings, when arrived 

 at maturity, is the best standard, as yet suggested, of their degree 

 of perfection or highness. We have also seen that, as the speciali- 

 sation of parts is an advantage to each being, so natural selection 

 will tend to render the organisation of each being more specialised 

 and perfect, and in this sense higher ; not but that it may leave 

 many creatures with simple and unimproved structures fitted for 

 simple conditions of life, and in some cases will even degrade or 

 simplify the organisation, yet leaving such degraded beings better 

 litted for their new walks of life. In another and more general 

 manner, new species become superior to their predecessors ; for they 

 have to beat in the struggle for life all the older forms, with which 

 they come into close competition. We may therefore conclude 

 that if under a nearly similar climate the eocene inhabitants of the 

 world could be put into competition with the existing inhabitants, 

 the former would be beaten and exterminated by the latter, as 

 would the secondary by the eocene, and the paleozoic by the 

 secondary forms. So that by this fundamental test of victory in 

 the battle for life, as well as by the standard of the specialisation of 

 organs, modern forms ought, on the theory of natural selection, to 

 stand higher than ancient forms. Is this the case? A large 

 majority of paleontologists would answer in the affirmative ; and it 

 seems that this answer must be admitted as true, though difficult of 

 proof. 



It is no valid objection to this conclusion, that certain Brachiopods 



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