APPEARANCE OF WHOLE GROUPS 355 



of species. If numerous species, belonging to the same gen- 

 era 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 process ; and the progeni- 

 tors 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 palaeonto- 

 logical evidence may be implicitly trusted; negative evidence 

 is worthless, as experience has so often shown. We contin- 

 ually 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 will 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. 



I may here recall a remark formerly made, namely, that it 

 might require a long succession of ages to adapt an organism 

 to some new and peculiar line of life, for instance, to fly 

 through the air; and consequently that the transitional forms 

 would often long remain confined to some one region ; but 

 that, when this adaptation had once been effected, and a few 

 species had thus acquired a great advantage over other or- 

 ganisms, a comparatively short time would be necessary to 

 produce many divergent forms, which would spread rapidly 

 and widely, throughout the world Professor Pictet, in his 

 excellent Review of this work, in commenting on early 

 transitional forms, and taking birds as an illustration, cannot 

 see how the successive modifications of the anterior limbs of 

 a supposed prototype could possibly have been of any advan- 

 tage. But look at the penguins of the Southern Ocean ; have 



