Appendix to Chapter V. 427 
However, be this as it may, I will now pass on to con- 
sider the difficulties and objections which have been brought 
against the theory on grounds of paleontology. 
These may be classified under four heads. First, the ab- 
sence of varietal links between allied species; second, the 
sudden appearance of whole groups of species—not only as 
genera and families, but even sometimes as orders and classes 
—without any forms leading up to them ; third, the occurrence 
of highly organized types at much lower levels of geological 
strata than an evolutionist would antecedently expect; and, 
fourth, the absence of fossils of any kind lower down than 
the Cambrian strata. 
Now all these objections depend on estimates of the im- 
perfection of the geological record much lower than that 
which is formed by Darwin. Therefore I have arranged the 
objections in their order of difficulty in this respect, or in the 
order that requires successively increasing estimates of the 
imperfection of the record, if they are to be successively 
answered. 
I think that the first of them has been already answered in 
the text, by showing that even a very moderate estimate of the 
imperfection of the record is enough to explain why interme- 
diate varieties, connecting allied speczes, are but comparatively 
seldom met with. Moreover it was shown that in some cases, 
where shells are concerned, remarkably well-connected series 
of such varieties have been met with. And the same applies 
to species and genera in certain other cases, as in the 
equine family. 
But no doubt a greater difficulty arises where whole groups 
of species and genera, or even families and orders, appear to 
arise suddenly, without anything leading up to them. Even 
this the second difficulty, however, admits of being fully met, 
when we remember that in very many cases it has been 
proved, quite apart from the theory of descent, that super- 
jacent formations have been separated from one another by 
