ORGANIC EVOLUTION 279 



crowd one another. Stake it out with markers at the 

 corners. Count the seedlings present and record the num- 

 ber, and note any peculiarities in their distribution. 



After allowing time for growth of several additional 

 leaves and a little differentiation in size among the seedlings, 

 count them again, this time in three classes, small, medium 

 and large, and record the numbers. 



Watch now the intensification of the struggle for existejice 

 and count the survivors of the three classes at longer inter- 

 vals through the season, and record the results. Count in 

 the end the individuals that are able to mature seed. 



Tabulate the results, showing what proportion of each 

 class fruited. 



Calculate the area that would have been required if all the 

 plants that germinated from seeds had attained the mini- 

 mum fruiting size ; if all had attained the maximum size of 

 the species. 



Artificial selection. — Man selects the variants he finds 

 among his cultivated species of animals and plants, not for 

 the good of the species, but for his own advantage. He 

 selects com for the starch or for the protein content of the 

 seeds. He selects cattle for beef or for milk production. 

 He selects fowls for egg production or for rapidity of 

 growth, or for form of comb and wattles (fig. 169) or for 

 color or sheen of plumage or for feathers or spurs on 

 the feet; and pigeons and gold fish he selects mainly for 

 qualities that suit his fancy. In the variability of living 

 organisms he finds resources, the value of which he is only 

 just beginning to comprehend. 



But, his improved varieties are all weaklings, incapable 

 of maintaining themselves in competition with the wild 

 races from which they are derived, and requiring to be isola- 

 ted and cared for, in order that the values for which they 

 are selected may be realized. High bred race horses are 



