Environment and Variation 65 



its equipment is tested by its success in the midst of the 

 environment, which is usually hostile in greater or less 

 degree. Now the equipment in question is mainly inherited 

 from ancestors who have previously tested it. This is 

 visibly true. But there are also seen in this equipment, from 

 time to time appearing, new things not previously known in 

 ancestral equipment, and however they may have originated 

 they immediately come under the test of use; and if they are 

 useful they are likely to become permanent, by exercise and 

 by cultivation, and by the survival or preferment of those 

 creatures possessed of them. 



That they arise in part by chance is not incompatible 

 with our knowledge of nature's methods. We see the in- 

 stinct of animals exercised in efforts for what must be called 

 chance results. And in fact there are few acts or processes 

 in nature which promise results with absolute certainty. So 

 that to achieve a thing it may become necessary, even with 

 volition to aid, to try experimentally several different acts, 

 and seize for development the one giving greatest oppor- 

 tunity. And much more is experiment usual, when volition 

 does not aid the action. 



Consider for example the method of a spider in con- 

 structing such a web as we sometimes see bridging a space 

 not accessible' to its power of locomotion, as when between 

 bushes on opposite sides of a brook. The animal resting 

 upon the foliage on one side perceives perhaps the general 

 proximity of the support opposite, and throws out a line of 

 its web to be carried by the wind. Now when we see it 

 later definitely attached, and supporting the finished net 

 upon some prominent twig we might suppose that twig to 



