Chap. IX. IMPEEFECTION OF GEOLOGICAL RECORD. 279 
CHAPTEE IX. 
On the Imperfection of the Geological Kecord. 
On the absence of intermediate varieties at the present day — On 
the nature of extinct intermediate varieties ; on tbeir number— 
On the vast lapse of time, as inferred from the rate of deposition 
and of denudation — On the poorness of our palasontological 
collections — On the intermittence of geological formations^— 
On the absence of intermediate varieties in any one formation — 
On the sudden appearance of groups of species — On their sudden 
appearance in the lowest known fossiliferous strata. 
In the sixth chapter I enumerated the chief objections 
which might be justly urged against the views main¬ 
tained in this volume. Most of them have now been 
discussed. One, namely the distinctness of specific 
forms, and their not being blended together by innu¬ 
merable transitional links, is a very obvious difficulty. 
I assigned reasons why such links do not commonly 
occur at the present day, under the circumstances ap¬ 
parently most favourable for their presence, namely 
on an extensive and continuous area with graduated 
physical conditions. I endeavoured to show, that the 
life of each species depends in a more important manner 
on the presence of other already defined organic forms, 
than on climate; and, therefore, that the really go¬ 
verning conditions of life do not graduate away quite 
insensibly like heat or moisture. I endeavoured, also, 
to show that intermediate varieties,- from existing in 
lesser numbers than the forms which they connect, will 
generally be beaten out and exterminated during the 
course of further modification and improvement. The 
main cause, however, of innumerable intermediate links 
not now occurring everywhere throughout nature de- 
