CHAPTER III 

 FOSSIL PEDIGREES 



"By dint of such great efforts we succeeded only in piecing together 

 genial romances more or less historical." — B. Grassi, Prof, of Compara- 

 tive Anatomy, Univ. of Rome, "La vita" (1906), p. 227. 



§ 1. The Argument in the Abstract 



The palaeontological argument for evolution is based upon 

 the observed gradual approximation in type of the earlier 

 forms of life, as represented by the fossils still preserved in 

 successive geological strata, to the later forms of life, as repre- 

 sented by the contemporary species constituting our present 

 flora and fauna. Here the observed distribution in time sup- 

 plements and confirms the argument drawn from mere struc- 

 tural affinity. Here we are no longer dealing with the spatial 

 gradation of contemporary forms, arranged on a basis of 

 greater or lesser similarity (the gradation whence the zoolo- 

 gist derives his argument for evolution), but with a temporal 

 gradation, which is simultaneously a morphological series and 

 an historical record. The lower sedimentary rocks contain 

 specimens of organic life very unlike modern species, but, the 

 higher we ascend in the geological strata, the more closely do 

 the fossil forms resemble our present organisms. In fact, the 

 closeness of resemblance is directly proportional to the prox- 

 imity in time, and this seems to create a presumption that 

 the later forms of life are the modified descendants of the 

 earlier forms. Considered in the abstract, at least, such an 

 argument is obviously more formidable than the purely an- 

 atomical argument based on the degrees of structural affinity 

 observable in contemporary forms. It ought, therefore, to 



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