Origin of Different Kinds of Adaptations 357 
Thus, from the point of view that is here taken, an animal 
does not become degenerate because it becomes parasitic, 
but the environment being given, some forms have found 
their way there; in fact, we may almost say, have been 
forced there, for these degenerate forms can only exist under 
such conditions. 
In conclusion, this much at least can be claimed for the 
mutation theory; that it meets with no serious difficulty in 
connection with the phenomena of degeneration. It meets 
with no difficulty, because it makes no pretence to, explain 
the origin of adaptations, but can account for the occurrence 
of degenerate forms, if it is admitted that these appear as 
mutations, or as definite variations. Let us, however, not 
close our eyes to the fact that there is still much to be 
explained in respect to the degeneration of animals and 
plants. It is far from my purpose to apply the mutation 
theory to all adaptations; in fact, it will not be difficult to 
show that there are many adaptations whose existence can 
have nothing directly to do with the mutation theory. 
PROTECTIVE COLORATION 
That many species of animals are protected by their re- 
semblance to their environment no one will probably deny. 
That we are ignorant in all cases as to how far this protec- 
tion is necessary for the maintenance of the species must be 
admitted. That some of the resemblances that have been 
pointed out have been given fictitious value, I believe very 
probable. 
Resemblance in color between the organism and its en- 
vironment has given to the modern selectionist some of his. 
most valuable arguments, but we should be on our guard 
against supposing that, because an animal may be protected 
by its color, the color has been acquired on this account. 
On the supposition that the animal has become adapted by 
