REVIEWS—ON THE ORIGIN OF SPECIES. 383 
breed freely, and produce fertile offspring ? This is the real question 
at issue; and, up to the present time, it has received no definite 
answer, except on the assumption that true species are separate and 
distinct creations, and are intended by the CreEatTor to remain 
distinct. 
Some of the most striking arguments in opposition to the trans- 
mutation theory, are based on geological revelations. These have 
been already referred to in a previous page, but as Mr. Darwin has 
devoted a separate chapter to their consideration at the portion of 
the work to which we have now arrived, we will briefly re-discuss 
them before closing ourreview. These geological arguments are two- 
fold: First, the non-occurrence of intermediate or transitionary forms 
in rock-strata ; and, secondly, the simultaneous occurrence, again and 
again, at various geological horizons, of entire groups of allied forms, 
distinct entirely (or for the greater part) from the organisms of lower 
and consequently earlier formed deposits. To make these points 
clear to our non-geological readers, we may observe, that, on each 
side of the Atlantic, we find certain beds entirely destitute of organic 
remains, underlying other beds in which these remains occur in great 
numbers. In some places it is difficult to draw an exact line of 
demarcation between the two, but that in no way affects our argu- 
ment. At acertain depth all fossils cease. Now, some observers, 
Mr. Darwin amongst others, believe that organic forms really existed 
during, and perhaps before, the deposition of these fossil-free strata. 
Many of these strata, it should be observed, are evidently much 
altered, by various chemical, igneous, or other agencies, from their 
original sedimentary condition ; and hence, fossils, if ever enclosed in 
them, may have become obliterated. Other strata of this fossil-free 
series, however, in various parts of the world, clearly retain their 
original characters, and do not differ, except in the absence of fossils, 
from many fossiliferous strata above them. From this fact, combined 
with the great thickness and extent of the rocks in question, most 
geologists consider these to be truly azote rocks, formed out of 
sediments deposited before the actual creation of living things. If 
this could be absolutely proved, the transmutation theory would re- 
ceive its death-blow: because in the strata which suceed or lie above 
these, and which constitute, be it remembered, the first or earliest 
fossiliferous strata really known, we ‘find various types appearing 
simultaneously ; and amongst these types we meet with various 
