384 REVIEWS—ON THE ORIGIN OF SPECIES. 
allied forms without any intermediate or truly transitionary links 
between them. If we cannot absolutely assert, however, that these 
Silurian forms (using the term Silurian in its extended sense) were 
the first created forms upon our earth, the weight of evidence is in 
favour, and strongly in favour, of that view. Hence, in common 
justice, the contrary hypothesis, resting as it does on purely negative 
evidence, ought not to be admitted into the discussion. But if we 
exclude it, what becomes of Mr. Darwin’s theory ? ‘If my theory 
be true,’ writes Mr. Darwin—‘‘it is indisputable that before the 
lowest Silurian stratum was deposited, long periods elapsed, as 
long as, or probably far longer, than the whole interval from the 
Silurian age'to the present day: and that during these vast yet 
quite unknown periods of time, the world swarmed -with living 
creatures.’ But if so, where are the remains of these ? Vast thick- 
nesses of rocky strata, formed during some at least of these periods, 
occur in various parts of the world, but as yet no fossils have been 
obtained from them; whilst the remains of forms which flourished 
afterwards, are entombed in thousands in the overlying rocks. It is 
not sufficient to urge, in refutation, that the lower limit of the fossil- 
bearing strata has been pushed lower and lower by the discovery of 
an obscure graptolite, here, and the fragment of a trilobite, there. 
To substantiate Mr. Darwin’s theory, something more than this is 
-clearly required. 
But passing over this weighty obstacle, we find in these geological 
revelations, others not less weighty. Above the Silurian formations, 
for example, we find another set of strata, to which, collectively, the 
term Devonian has been applied, and in which the fossils (with very 
few exceptions) are entirely different. Above the Devonian beds again, 
we come upon the Carboniferous with another distinct series of organic 
‘ remains; and so on successively, through various other groups of 
strata, each representing a certain period of time during which it was 
under process of deposition in the form of muddy, sandy, or calcareous 
sediments. In these sediments, moreover, a portion of the flora and 
fauna of the period (¢d est: of the plants and animals then living) was 
entombed, and so preserved to us: just as we see, at the present day, 
the leaves, shells, bones, &c., of existing organisms, enclosed in sedi- 
ments under process of deposition in seas, lakes, and estuaries. Now, 
on the hypothesis of distinct acts of creation, there is nothing unac- 
countable in the sudden appearance, successively, of these distinct sets 
