Chap. IX. GEOLOGICAL RECOED. 303 



probably elapsed between our consecutive formations, — 

 longer perhaps in some 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 or some few parent-forms ; and in the 

 succeeding formation such species will appear as if sud- 

 denly 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 ; but that when this had 

 been effected, and a few species had thus acquired a 

 great advantage over other organisms, a comparatively 

 short time would be necessary to produce many di- 

 vergent forms, which would be able to spread rapidly 

 and widely throughout the world. 



I will now give a few examples to illustrate these 

 remarks ; and to show how liable we are to error in 

 supposing that whole groups of species have suddenly 

 been produced. I may recall the well-known fact that 

 in geological treatises, published not many years ago, 

 the great class of mammals was always spoken of as 

 having abruptly come in at the commencement of the 

 tertiary series. And now one of the richest known 

 accumulations of fossil mammals belongs to the middle 

 of the secondary series ; and one true mammal has 

 been discovered in the new red sandstone at nearly the 

 commencement of this great series. Cuvier used to 

 urge that no monkey occurred in any tertiary stratum ; 

 but now extinct species have been discovered in India, 

 South America, and in Europe even as far back as the 

 eocene stage. The most striking case, however, is that 

 of the Whale family ; as these animals have huge bones, 

 are marine, and range over the world, the fact of not 

 a single bone of a whale having been discovered in 



