FUNDAMENTAL PRINCIPLES I9I 



the result if all the seeds produced by one of our large 

 forest trees were able to mature. And yet the total 

 number of any given kind of fern, of hedge mustard, or 

 of forest tree does not appreciably change from year to 

 year. The reason, of course, is that not all of the spores 

 and seeds produced are allowed to come to maturity. 

 The direct result of the enormous number of spores and 

 seeds produced is a struggle for existence — for sufficient soil, 

 water, light, and food to insure a healthy, mature plant. 



174. Elimination of the Unfit. — As a result of variation 

 certain individuals will succeed better than others in the 

 struggle for existence. Those most poorly adapted to 

 their surroundings will perish, and only the more vigorous 

 ones — those best adjusted to their surroundings — will 

 persist. The result of this struggle for existence was 

 called by Herbert Spencer the ^^ survival of the fittest.'' 

 What really takes place in nature is the elimination, by 

 death, of the unfit. Darwin called this natural selection, 

 implying that the result is similar to that when plant 

 breeders select out of a progeny the best individual for 

 further breeding. What really takes place in nature, 

 however, is not so much the selection of the fittest, but a 

 rejection of the unfit. Thus, among the 50,000,000 

 progeny of a single fern-plant, some are sure to have a 

 weaker constitution than others; to develop a weaker root- 

 system, less chlorophyll in their leaves, a less number 

 of sporophylls or spores, or to be inferior in other ways. 

 The result will be that, in the course of only a few years, 

 the descendants of the most vigorous or otherwise superior 

 plants will alone be left to perpetuate the race. 



175. Problems to Solve. — In the preceding paragraphs 

 we have called attention to a number of the problems 



