76 ABSENCE OF INTERMEDIATE VARIETIES [Chap. X. 



would intervene dnring such lengthy periods; and in 

 these cases the inhabitants of the archipelago would 

 migrate, and no closely consecutive record of their 

 modifications could be preserved in any one formation. 



Very many of the marine inhabitants of the archi- 

 pelago now range thousands of miles beyond its con- 

 fines ; and analogy plainly leads to the belief that it 

 would be chiefly these far-ranging species, though only 

 some of them, which would oftenest produce new 

 varieties ; and the varieties would at first be local or 

 confined to one place, but if possessed of any decided 

 advantage, or when further modified and improved, they 

 would slowly spread and supplant their parent-forms. 

 When such varieties returned to their ancient homes, 

 as they would differ from their former state in a nearly 

 uniform, though perhaps extremely slight degree, and 

 as they would be found embedded in slightly different 

 sub-stages of the same formation, they would, according 

 to the principles followed by many palaeontologists, be 

 ranked as new and distinct species. 



If then there be some degree of truth in these re- 

 marks, we have no right to expect to find, in our 

 geological formations, an infinite number of those fine 

 transitional forms which, on our theory, have connected 

 all the past and present species of the same group into 

 one long and branching chain of life. We ought only 

 to look for a few links, and such assuredly we do find 

 — some more distantly, some more closely, related to 

 each other ; and these links, let them be ever so close, 

 if found in different stages of the same formation, 

 would, by many palajontologists, be ranked as distinct 

 species. But I do not pretend that I should ever have 

 suspected how poor was the record in the best preservecl 



