Appendix to Chapter V. 429 
cases are neither few nor unimportant, and therefore they 
deprive the objection of the force it would have had if the 
selected cases to the contrary were the general rule. 
In addition to these considerations, the following, some of 
which are of a more special kind, appear to me so important 
that I will quote them almost 27 extenso. 
We continually forget how large the world is, compared with 
the area over which our geological formations have been care- 
fully examined: we forget that groups of species may elsewhere 
have long existed, and have slowly multiplied, before they in- 
vaded the ancient archipelagoes of Europe and the United States. 
We donot make due allowance for the intervals of time which 
have elapsed between our consecutive formations,—longer per- 
haps in many cases than the time required for the accumulation 
of each formation. These intervals will have given time for the 
multiplication of species from some one parent form ; and, in 
the succeeding formation, such groups of species will appear as 
if suddenly created. 
I may here recall a remark formerly made, namely, that it 
might require a long succession of ages, to adapt an organism 
to some new and peculiar line of life, for instance, to fly through 
theair; and consequently that the transitional form would often 
long remain confined to some one region; but that, when this 
adaptation had once been effected, and a few species had thus 
acquired a great advantage over other organisms, a compara- 
tively short time would be necessary to produce many divergent 
forms, which would spread rapidly and widely throughout the 
world.... 
In geological treatises, published not many years ago, 
mammals were always spoken of as having abruptly come in at 
the commencement of the tertiary series. And now one of the 
richest known accumulations of fossil mammals belongs to the 
middle of the secondary series; and true mammals have been 
discovered in the new red sandstone at nearly the commence- 
ment of this great series. Cuvier used to urge that no monkey 
occurred in any tertiary stratum; but now extinct species have 
been discovered in India, South America, and in Europe as far 
