Chap. XIV. 
RECAPITULATION. 
471 
larger groups tend to give birth to new and dominant 
forms; so that each large group tends to become still 
larger, and at the same time more divergent in character. 
But as all groups cannot thus succeed in increasing in 
size, for the world would not hold them, the more domi¬ 
nant groups beat the less dominant. This tendency 
in the large groups to go on increasing in size and 
diverging in character, together with the almost in¬ 
evitable contingency of much extinction, explains the 
arrangement of all the forms of life, in groups sub¬ 
ordinate to groups, all within a few great classes, which 
we now see everywhere around us, and which has pre¬ 
vailed throughout all time. This grand fact of the 
grouping of all organic beings seems to me utterly 
inexplicable on the theory of creation. 
As natural selection acts solely by accumulating 
slight, successive, favourable variations, it can produce 
no great or sudden modification; it can act only by 
very short and slow steps. Hence the canon of Natura 
non facit saltum,” which every' fresh addition to our 
knowledge tends to make truer, is on this theory simply 
intelligible. We can plainly see why nature is prodigal 
in variety, though niggard in innovation. But why this 
should be a law of nature if each species has been in¬ 
dependently created, no man can explain. 
Many other facts are, as it seems to me, explicable 
on this theory. How strange it is that a bird, under 
the form of woodpecker, should have been created to 
prey on insects on the ground; that upland geese, 
which never or rarely swim, should have been created 
with webbed feet; that a thrush should have been 
created to dive and feed on sub-aquatic insects; and 
that a petrel should have been created with habits and 
structure fitting it for the life of an auk or grebe! and 
so on in endless other cases. But on the view of each 
