The Problem of Adaptation 9 
theless, if the color is useful.to its possessor, it is an adapta- 
tion in our s-nse of the word, without regard to the way in 
which it has been acquired. Even, for instance, if the resem- 
blance were purely the outcome of chance in the sense that 
the color appeared without relation to the surroundings, it 
would still be an adaptation if it were of use to the animal 
under the ordinary conditions of life. 
In the lower groups numerous cases in which. animals 
resemble their surroundings could be given. Such cases are 
known in crustacea, worms, mollusks, hydroids, etc., and the 
possible value of these resemblances may be admitted in 
many instances. 
It is rather curious that so few cases of adaptive color- 
ation have been described for plants. No one supposes 
that the.slate color of the lichen is connected with the color 
of the rocks.on which it grows, in the sense that the resem- 
blance is of any use to the lichen. Nor-does the color of the 
marine red algz serve in any way to protect the plants so 
far as is known. The green color of nearly all the higher 
plants is obviously connected with the substance, chlorophyl, 
that is essential for the processes of assimilation, and has 
no relation to external objects. But when we come to the 
colors of flowers we meet with curious cases of adaptation, 
at least according to the generally accepted point of view. 
For it is believed by many naturalists that the color of the 
corolla of flowering plants is connected with the visits of 
insects to the flowers, and: these visits are in many cases 
essential for the cross-fertilization of the flowers. This adap- 
tation is one useful to the species, rather than the individual, 
and belongs to another category. 
The leaf of the: Venus’s fly-trap, which suddenly closes 
together. from the sides when a fly or other light body 
comes to rest on it, is certainly a remarkable adaptation. 
A copious secretion of a digestive. fluid is poured out on the 
surface of the leaf, and the products of digestion are absorbed. 
