OBJECTIONS TO THE THEORY OF DESCENT. 333 



very many fossil species are known and named from single 

 and often broken specimens, or from a few specimens 

 collected on some one spot. Only a small portion of the 

 surface of the earth has been geologically explored, and 

 no part with sufficient care, as the important discoTeries 

 made every year in Europe prove. No organism wholly 

 soft can be preserved. Shells and bones decay and dis- 

 appear when left on the bottom of the sea, where sediment 

 is not accumulating. We probably take a quite erroneous 

 view, when we assume that sediment is being deposited 

 over nearly the whole bed of the sea, at a rate sufficiently 

 quick to imbed and preserve fossil remains. Throughout 

 an enormously large proportion of the ocean, the bright 

 blue tint of the water bespeaks its purity. The many 

 cases on record of a formation conformably covered, after 

 an immense interval of time, by another and later format 

 tion, without the underlying bed having suffered in the 

 interval any wear and tear, seem explicable only on the 

 view of the bottom of the sea not rarely lying for ages in 

 an unaltered condition. The remains which do become 

 imbedded, if in sand or gravel, will, when the beds are 

 upraised, generally be dissolved by the percolation of 

 rain-water charged with carbonic acid. Some of the many 

 kinds of animals which live on the beach between high 

 and low water mark seem to be rarely preserved. For 

 instance, the several species of the Ghthamalinm (a sub- 

 family of sessile cirripeds) coat the rocks all over the world 

 in infinite numbers : they are all strictly littoral, with 

 the exception of a single Mediterranean species, which 

 inhabits deep water, and this has been found fossil in 

 Sicily, whereas not one other species has hitherto been 

 found in any tertiary formation ; yet it is known that 

 the genus Chthamalus existed during the Chalk period. 

 Lastly, many great deposits, requiring a vast length of 



