The Problem of Adaptation 19 
cases the color may not serve this purpose, or any purpose 
at all. Thus while in the former case we speak of the color 
as an adaptation to the surroundings, in the latter we do not 
think of it as having any connection at all with the environ- 
ment. Even in the same animal the color of different parts 
of the body may appear under this twofold relation. For 
example, the green color of the skin of the frog renders it 
less conspicuous amongst the green plants on the edge of 
the stream, but the brilliant orange and black pigment in the 
body-cavity cannot be regarded as of any use to the animal. 
ADAPTATIONS FOR THE GOOD OF THE SPECIES 
Aside from the class of adaptations that are for the good 
of the individual, there is another class connected solely 
with the preservation of the race. The organs for reproduc- 
tion are the most important examples of this kind. These 
organs are of no use to the individual for maintaining its own 
existence, and, in fact, their presence may even be deleterious 
to the animal. The instincts connected with the use of these 
organs may lead inevitably to the death of the individual, 
as in the case of the California salmon, which, on entering 
fresh water in order to deposit its eggs, dies after performing 
this act. 
The presence of the organs of reproduction in the indi- 
vidual is obviously connected with the propagation of other 
individuals. Indeed in many organisms the life of the 
individual appears to have for its purpose the continuation 
of the race. In a large number of animals the individual 
dies after it has deposited its eggs. The most striking case 
is that of the May-flies, whose life, as mature individuals, may 
last for only a few hours. The eggs are set free by the 
bursting of the abdomen, and the insect dies. The male 
bee also dies after union with the queen. In some annelids, 
the body is also said to burst when the eggs are set free; 
