CiiAP. IX. GROUPS OF ALLIED SPECIES. 287 



forf^ot that g-ioups of species may elsewhere have long: 

 existed, and liavc slowly multiplied, before they invaded 

 the ancient archipela^^oes of Europe and the United States. 

 We do not make due allowance for the enormous intervals 

 of time which have elapsed between our consecutive forma- 

 tions — loiiocr perhaps in many cases than the time required 

 for the accumulation of each formation. These intervals 

 will have g-iven time for the multiplication of species from 

 some one or some few parent-forms ; and in the succeeding^ 

 formation such groups of 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 or- 

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

 lo liy through the air; and consequently that the transition- 

 al forms would often 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 organisms, a comparatively short time would 1)0 neces- 

 sary to produce many divergent forms, ■which would spread 

 rapidly and widely throughout the world. Prof. 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 ante- 

 rior limbs of a supposed protot\'pe could possibly have been 

 of any advantage. But look at the penguins of the Southern 

 Ocean; have not these birds their front limbs in this precise 

 intermediate state of "neither true arms nor true wings?" 

 Yet these birds hold their place victoriously in the battle 

 for life; for they exist in infinite numbers and of many kinds. 

 I do not suppose that we here see the real transitional 

 grades through which the wings of birds have passed ; but 

 what special dilliculty is there in believing that it might 

 profit the modified descendants of the ]ienguin, first to become 

 enabled to flap along the surface of the sea like the logger- 

 headed duck, and ultimately to rise from its surface and glide 

 through the air? 



I will now give a fmv examples to illustrate the fore- 

 going remarks, and to show how liable we are to error in 

 supposing that whole groups of sj^ecies have suddenly been 

 produced. Even in so short an interval as that between the 

 iirst and second editions of Pictet's great work on Paleon- 

 tologv, pu])lished in 18-i4-'4G and in ISSS-^o?, the conclusions 



