226 EXPERIMENTAL GENERAL SCIENCE 



ferences they present. This tendency toward variation which 

 all organic life seems to possess makes it possible for some 

 groups to outstrip others in the race for life. We can readily 

 understand that in case a given species or race of animals or 

 plants finds itself in surroundings where the conditions of 

 life are growing increasingly difficult, the group whose varia- 

 tions are most favorable to their success is the group likely 

 in the long run to survive. When an area becomes over- 

 populated, for instance, the race with the ability to quickly 

 move into new regions and adjust itself to the conditions there, 

 might not only survive, but originate new lines of descent. 



192. The Struggle for Existence. The fact which makes 

 variation in animals and plants of much importance is the 

 tendency which every species has to produce more young 

 than can possibly come to maturity. A single fern leaf may 

 produce several million spores in a season, and the plant may 

 have several such leaves, while a single locality may contain 

 thousands of fern plants. If every spore should grow into a 

 new fern with spores of its own, and so on, it would only be a 

 few years before there would be enough of this single species 

 to thickly populate every square foot of the earth's surface. 

 Such a thing is not likely to occur, however, because every 

 other form of life is similarly attempting to conquer the world 

 for itself. This can only result in a vigorous struggle for 

 existence in which the strongest and best fitted to survive 

 are practically the only ones that do so. In such a struggle, 

 however, a fortunate variation may save a form from extinc- 

 tion by enabling it to overcome the forces opposed to it. 

 When this phase of the subject is brought to his attention, the 

 most casual observer will be able to recall evidences of such a 

 struggle. Animals, as we know, constantly feed on plants, 

 but the plants even up matters to some extent by feeding on 

 animals, for the diseases that afflict animals, including man, 

 are nearly all of plant origin. Plants struggle with plants, 



