82 THE ORIGIN OF SPECIES 



varieties would merely appear as so many new, though 

 closely allied species. It is also probable that each great 

 period of subsidence would be interrupted by oscillations 

 of level, and that slight climatal changes would inter- 

 vene during 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 archipel- 

 ago now range thousands of miles beyond its confines; 

 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 

 difiier from their former state in a nearly uniform, though 

 perhaps extremely slight degree, and as they would be 

 found imbedded in slightly different sub-stages of the 

 same formation, they would, according to the principles 

 followed by many paleontologists, 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 



