336 DARWINISM STATED BY DARWIN HIMSELF. 

 SUDDElf APPEARANCE OE GROUPS OF ALLIED SPECIES. 



Orma of The abrupt manner in which whole groups 



Species, of species suddenly appear in certain forma. 

 ^^^^ ■ tions has been urged by several paleontolo- 

 gists — for instance, by Agassiz, Pictet, and Sedgwick — 

 as a fatal objection to the belief in the transmutation of 

 species. If numerous species, belonging to the same 

 genera or families, have really started into life at once, 

 the fact would be fatal to the theory of evolution through 

 natural selection. For the development by this means 

 of a group of forms, all of which are descended from some 

 one progenitor, must have been an extremely slow pro- 

 cess ; and the progenitors must have lived long before 

 their modified descendants. But we continually overrate 

 the perfection of the geological record, and falsely infer, 

 because certain genera or families have not been found 

 beneath a certain stage, that they did not exist before 

 that stage. In all cases positive paleontological evidence 

 may be implicitly trusted ; negative evidence is worthless, 

 as experience has so often shown. We continually forget 

 how large the world is, compared with the area over 

 which our geological formations have been carefully ex- 

 amined ; we forget that groups of species may elsewhere 

 have long existed, and have slowly multiplied, before 

 they invaded the ancient archipelagoes of Europe and 

 the United States. We do not make due allowance for 

 the intervals of time which have elapsed between our 

 consecutive formations — longer, perhaps, in many cases 

 than the time required for the accumulation of each 

 formation. These intervals wiU have given time for the 

 multiplication of species from some one parent-form ; 

 and, in the succeeding formation, such groups or species 

 will appear as if suddenly created. 



