1894. | 883 [ Poulton. 
but they differed from these latter in that they had extremely 
small brains. We can easily understand that inferiority of intel- 
lect would cause them to be worsted by animals which were in 
other respects no better endowed. 
Exactly parallel is the relation of man and the apes. In bodily 
structure the difference is insignificant. In the brain, however, 
we meet an important and essential distinction. It would appear 
‘here that natural selection has taken one particular part of the 
organism of paramount importance in the struggle, and has 
developed that rather than made a change along the whole line. 
We see the same relationship in the gigantic reptiles of the 
secondary period as compared with the mammals of the Tertiary. 
The latter with their larger brains and higher intelligence were 
able to supplant the former, just as they have in turn been sup- 
planted by the still larger brained animals whose descendants now 
people the earth. All this seems to me to afford very strong 
support to the theory of natural selection. 
Passing now to another class of objections: natural selection, 
it is said, can never account for the beginnings of things. Until 
an organ is raised to a useful level, selection can have nothing to 
do with it. At first sight that is a serious objection, but it 
suggests its own answer; viz., that an organ so rarely develops 
ab initio. Organs are not formed anew in an animal, but they 
are formed by the modification of pre-existing organs; so that, 
instead of having one beginning for each organ, we have to push 
the beginning further and further back, and find that a single 
origin accounts for several successive organs, or at any rate 
several functions instead of one. 
The typical vertebrate has four limbs. These in fishes are 
used for swimming, while in terrestrial forms the same limbs are 
modified and used for walking. New organs are not introduced, 
but the old are modified for a new purpose. When the terres- 
trial form again becomes aquatic, the limb that was used for 
terrestrial progression is modified back into a functional fin; and 
again, when flight becomes necessary, the same organ is used for / 
the new function. So that whatever the changes in the mode of 
progression, we need no new organ at all; for the old organ | 
used for the new purpose. It is very much easier to understar 
how a useful level can be attained in that way than by org; 
starting ab initio. But of course we must come down to a 
