BNDONOMIC AND HETERONOMIC SELECTION. II 7 



habits, as was the case in the original home. This is an illustration 

 of what I call " habitvdinal selection." We shall next consider an 

 illustration of aptitudinal selection, which will be gained by changing 

 the illustration just given at one point. Instead of taking the two 

 individuals which start the two colonies from those which for a genera- 

 tion have been feeding on different kinds of trees, we must take them 

 from two separate strains which have, for many generations, had 

 their separate methods of feeding, so that not only their habitudes 

 but their aptitudes must be somewhat different. Again, we may 

 consider conditions that would produce what we might call "acci- 

 dental selection." This might occur if the two individuals starting 

 the two colonies were from the same strain and had both of them 

 gained various experiences by feeding on different trees, so that their 

 habits were not fixed. One of them we will suppose was brought by 

 accident to a fine grove of candle-nut trees in the new district, and for 

 a hundred years finds no cause to go elsewhere; while the other one, 

 in another valley, is brought to a grove of what the Hawaiians call 

 ohia trees, and there remains for an equal number of years. Is it not 

 certain that the selection will be somewhat divergent; and to what 

 determining cause shall we attribute the divergence if not to accidents 

 that started these individuals of varied attainments in separate colo- 

 nies, and in groves of different kinds of trees? As the valleys are 

 near together and on the same side of the mountain range, the rain- 

 fall and other features of climate must be essentially the same. If 

 the creatures under consideration were insects endowed with higher 

 powers for exploring the environment, I recognize that accidents of 

 the kind here suggested would have little or no effect in determining 

 the forms of selection ; for, in such cases, sHght differences of aptitudes 

 or habitudes would be sure to control the method of using the environ- 

 ment. Moreover, such species would not fall into isolated groups 

 through their occupying separate valleys. When an isolated individ- 

 ual or pair deals with an environment possessing resources that are 

 varied but familiar and easily explored, previous habitudes and apti- 

 tudes are the chief factors controlling the methods of using the 

 environment. If the power of using different resources is great 

 and the power of exploration small, the method of using the envi- 

 ronment may be determined by the kind of resources first reached 

 on entering the district. 



Heteronomic selection is of two forms — natural selection, produced by 

 conditions in the environment that are independent of any purpose to 

 control the forms of survival, and artificial selection, which is deter- 

 mined by more or less distinct purpose to control survival. If in the 



