I believe safely inferred <that> groups of marine <?> fossils only preserved for future ages where sediment goes on long <and> continuous<ly> and with rapid but not too rapid deposition in <an> area of subsidence. In how few places in any one region like Europe will <?> these contingencies be going on? Hence <?> in past ages mere [gaps] pages preserved{114}. Lyell'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{115}? We know then cattle existed. Compare number of living,--immense duration of each period,--fewness of fossils. {114} See Note 3, p. 27. {115} 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." 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 formation 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 suddenly,--but in [later] tertiary not quite suddenly{116}, 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. {116} 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.