422 Darwin, and after Darwin. 
formed at all. We have already noticed in the text that it is 
only the more or less hard parts of organisms which under 
any circumstances can be fossilized; and even the hardest 
parts quickly disintegrate if not protected from the weather 
on land, or from the water on the sea-bottom. Moreover, as 
Darwin says, “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 embed 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 a later formation, 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.” 
Next, as regards littoral animals, he shows the difficulty 
which they must have in becoming fossils, and gives a 
striking example in several of the existing species of a sub- 
family of cirripedes (Ch/hamaline), “ which coat the rocks all 
over the world in infinite numbers,” yet, with the exception of 
one species which inhabits deep water, no vestige of any of 
them has been found in any tertiary formation, although it is 
known that the genus Ch/hamalus existed through the Chalk 
period. Lastly, “with respect to the terrestrial productions 
which lived through the secondary and palzozoic periods, it 
is superfluous to state our evidence is fragmentary in an 
extreme degree. For instance, until recently not a land 
shell was known belonging to either of these vast periods,” 
with one exception; while, “in regard to mammiferous 
remains, a glance at the historical table in Lyell’s Manual 
will bring home the truth, how accidental and rare has been 
their preservation, far better than pages of detail. Noor is their 
rarity surprising, when we remember how large a proportion 
of the bones of tertiary mammals have been discovered either 
