26 GEOLOGY 



past ages mere [gaps] pages preserved 1 . Ly ell's 

 doctrine carried to extreme, we shall understand 

 difficulty if it be asked: what chance of series of 

 gradation between cattle by (illegible) at age (illegible) 

 as far back as Miocene 2 ? We know then cattle 

 existed. Compare number of living, immense dura- 

 tion of each period, fewness of fossils. 



This only refers to consecutiveness of history of 

 organisms of each formation. 



The foregoing argument will show firstly, that 

 formations are distinct merely from want of fossils 

 (of intermediate beds), and secondly, that each for- 

 mation is full of gaps, has been advanced to account 

 for fewness of preserved organisms compared to 

 what have lived on the world. The very same 

 argument explains why in older formations the 

 organisms appear to come on and disappear sud- 

 denly, but in [later] tertiary not quite suddenly 3 , 

 in later tertiary gradually, becoming rare and 

 disappearing, some have disappeared within man's 

 time. It is obvious that our theory requires gradual 

 and nearly uniform introduction, possibly more 

 sudden extermination, subsidence of continent of 

 Australia &c., &c. 



Our theory requires that the first form which 

 existed of each of the great divisions would present 

 points intermediate between existing ones, but im- 

 mensely different. Most geologists believe Silurian 4 

 fossils are those which first existed in the whole world, 



1 See Note 3, p. 27. 



2 Compare Origin, Ed. i. p. 298, vi. p. 437. "We shall, perhaps, best 

 perceive the improbability of our being enabled to connect species by 

 numerous, fine, intermediate, fossil links, by asking ourselves whether,' for 

 instance, geologists at some future period will be able to prove that our 

 different breeds of cattle, sheep, horses, and dogs have descended from a 

 single stock or from several aboriginal stocks." 



! The sudden appearance of groups of allied species in the lowest known 

 fossiliferous strata is discussed in the Origin, Ed. i. p. 306, vi. p. 446. The 

 gradual appearance in the later strata occurs in the Origin, Ed. i. 

 p. 312, vi. p. 453. 



4 Compare Origin, Ed. i. p. 307, vi. p. 448. 



