IN EVOLUTION FROM A GEOLOGICAL POINT OF VIEW. I71 
are species—not as regards their outside limits, but as 
regards their essence? They are assemblages of vast 
multitudes of similar beings, lasting certainly for very many 
generations, sometimes even for geological periods, which, 
though constantly, it may be, subject to small individual 
variations, yet remain so essentially alike, that they must be 
regarded throughout the term of their existence as one and 
the same kind of animal—such that the action of evolution 
must on the whole be said to be either arrested or imper- 
ceptible within them. Granted that evolution may be 
traceable in their varieties or in their connections with 
kindred species, yet, to say the least, their existence at all 
means nothing else than the constant retardation of 
evolutionary action. It asserts that evolution at most can 
only act by steps and not continuously. But this cannot be 
the ideal of evolution! If that were the sole agent in the 
advance of nature, it seems only conceivable that it should 
act so equably and uniformly, that the whole advance 
should be by infinitesimal variation all through; that in the 
present nature there should exist no specific persistence of 
forms and no specific limits except those caused by 
accidental breaks or failures, which, in their turn, should 
always tend to eradicate themselves again; that within any 
one species development should be so constantly and 
uniformly going on, as, normally and continuously, to expand 
its amount of variation without splittmg it up by new 
specific limits. In fact evolution ought @ priori to be 
supposed to produce the obliteration, not the multiplication, 
of species. 
5 (28). Further the existence of set species is a phenomenon 
not only of the recent period, but of all known geological ages. 
We acknowledge fully the imperfection of the Geological 
Record, but at least it is congruous with the better known 
Recent Period in the nature of its specific limitations. No 
doubt fossil species are occasionally found in a state of 
disintegration: occasionally tco this state tends to their 
splitting into sections which may in cases be traceable as the 
ancestry of distinct species ina subsequent age. Thus far, 
it may be granted, there is some amount of evidence for 
evolutionary change. But all this is a very small exception 
(as far as is hitherto known) compared with the stability of 
the species at any known geological level. The general 
rule is to find kindred species, rich in individuals, con- 
temporary in one age or consecutive in more than one, 
