472 THE EVOLUTION OF LIFE. 



"We next considered " the Arguments from Morphology." 

 Leaving out those kinships among organisms disclosed by 

 their developmental metamorphoses, the kinships which their 

 adult forms show are profoundly significant. The remarkable 

 unities of type which are found under such different exter- 

 nals, are inexplicable except as residts of community of de- 

 scent with non-community of modification. Again, each 

 organism analyzed apart, shows us, in the likenesses obscured 

 by unlikenesses of its component parts, a peculiarity of struc- 

 ture that can be ascribed only to the formation of a more 

 heterogeneous organism out of a more homogeneous one. 

 And once more, the habitual existence of rudimentary organs, 

 homologous with organs that are developed in allied animals 

 or plants, while it admits of no other rational interpretation, 

 has a satisfactory interpretation given to it by the hypo- 

 thesis of evolution. 



Last of the inductive evidences, came " the Arguments from 

 Distribution." While the phenomena of distribution in 

 Space, prove to be unaccountable as results of designed adapt- 

 ation of organisms to their habitats, they prove to be 

 accountable as results of the competition of species, and the 

 spread of the superior into the habitats of the inferior, fol- 

 lowed by the changes which new conditions induce. Though 

 the phenomena of distribution in Time, are so fragmentary 

 that no positive conclusion can be drawn from them ; yet all 

 of them are reconcileable with the hypothesis of evolution, and 

 some of them yield it strong support — especially the near 

 relationship that exists between the living and extinct 

 types of each great geographical area. 



In each of these four groups, we thus found several argu- 

 ments which point to the same conclusion; and the con- 

 clusion pointed to by the arguments of any one group, is that 

 pointed to by the arguments of all the other groups. This 

 coincidence of coincidences, would give to the induction a 

 very high degree of probability, even were it not enforced 

 by deduction. 



