86 THE CHAIN OF LIFE. 



elsewhere ad<luced at length,^ in my judgment altogether 

 subverts the prevalent theory of " survival of the fittest," and 

 shows that the struggle for existence, so far from being a cai^se 

 of development and improvement, has led only to decay and 

 extinction, whereas the advent of new and favourable condi- 

 tions, and the removal of severe competition, are the circum- 

 stances favourable to introduction of new and advanced 

 species. This testimony of the invertebrates of the sea we 

 shall find is confirmed by other groups of living beings, to be 

 noticed in the sequel. 



Note.— Since writing the above chapter the author has received the 

 important memoir of Barrande on the Silurian Brachiopods, in which, as 

 tho result of the most elaborate and detailed comparisons, he concludes 

 that in the case of these shells, as in that of the Cephalopods and Tnlobites, 

 the introduction of species in geological time has not occurred by modifi- 

 cation, but must have depended on a creative process. It is such painstaking 

 researches as those of the great Bohemian palaeontologist which must finally 

 settle these questions, in so far as geology is concerned. 



Professor Whitfield has announced [Am. yi. of Science, Jan. i»»o) the 

 discovery of remains of Decapod Crustaceans in the Devonian or Erian of 

 Ohio; thus carrying back this form of life one stage farther, and making 

 the highest Crustaceans still more distinctly contemporaneous w:th the 

 Trilobites. 



^ Report on Devonian Fossil Plants of Canada, 187 1. Story of the 

 Earth and Man, 1873. Address to American Association, 1875. 



