604 LAWS OF ORGANIC DEVELOPMENT. 
in swamps surrounded by water, and compelled to assume a more 
or less aquatic life. Another case which has also probably often 
occurred, would be when the enemies of a species might so increase 
as to compel a large number of the latter to combat who would 
previously have escaped it. 
In these cases the structure produced would be necessarily 
adaptive. But the effect would be most frequently to destroy or 
injure the animals (retard them) thus brought into new situations — 
and compelled to an additional struggle for existence, as has, no 
doubt, been the case in geologic history. Preservation, with mod- 
ifications would only ensue where the changes should be introduced 
very gradually. This mode is always a consequence of the op- 
tional use. The cases here included are those where choice se- 
lects from several alternatives, thus exercising its influence on 
structure. Choice will be influenced by the emotions, the imagina- 
tion, and by intelligence. 
As examples of intelligent selection the modified organisms of 
the varieties of bees and ants must be regarded as striking exam- 
ples of its exercise. Had all in the hive or hill been modified 
alike, as soldiers, queens, etc., the origin of the structures might 
have been thought to be compulsory ; but varied and adapted as 
the different forms are to the wants of a community, the influence 
of intelligence is too obvious to be denied. The structural results 
are obtained in this case by a shorter road than by inheritance. 
The selection of food offers an opportunity for the exercise of 
intelligence, and the adoption of means for obtaining it still 
greater ones. It is here that intelligent selection proves its su- 
premacy as a guide of use, and consequently of structure, to all 
the other agencies here proposed. The preference for vegetable 
or for animal food determined by the choice of individual animals 
among the omnivores, which were, no doubt, according to the palæ- 
ontological record the predecessors of our herbivores, and per 
haps of carnivores also, must have determined their course of 
life and thus of all their parts into those totally distinct di- 
rections. The choice of food under ground, on the ground, or in 
the trees would necessarily direct the uses of organs in those di- 
rections respectively. 
Intelligence is a conservative principle and always will direct 
effort and use into lines which will be beneficial to its possessor. 
Thus we have the source of the fittest—i.e., addition of parts 
by increase and location of growth force directed by the will— 
