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 ; 



