278 GENERAL BIOLOGY 



Fitness. Fitness for natural selection consists in two 

 things : 



1) Ability to get a living and to reach maturity; this is 

 provision for individual needs. 



2) Ability to leave well equipped descendents possessed 

 of like good qualities. This is provision for the future of the 

 race. It is not, therefore, the superior excellence of a par- 

 ticular organ, but the balanced excellence of the organism 

 as a whole that is of determinative value. Good leg muscles 

 doubtless make for speed ; but speed alone will not avail the 

 hunted hare, if it have not also endurance and instincts of 

 self preservation. "The race is not always to the swift." 

 And all these will be of no moment whatever from the point 

 of view of evolution if it leave no well born descendents. For 

 the sterile variety "carries its own death warrant." What 

 has a chance of survival, therefore, under the most rigid 

 natural selection, will depend on what variation of the 

 several parts of the body appear, and in what combination. 



Study 36. The struggle for existence among seedlings. 



This study is one that requires time, and observations at 

 repeated intervals; the struggle for existence is not a 

 matter of laboratory periods. Seedling plots of ground, 

 thickly sown by nature to annual weeds are always to be 

 found in the corners of neglected gardens, by roadsides 

 and in fence rows. Other plots in wet, shaded places by 

 streams are overgrown annually by wild touch-me-nots 

 (Impatiens), and in sunny places by smartweeds (Poly- 

 gonum) . If for want of time this study be deemed unavail- 

 able for class use, it may be carried out by anyone in his 

 home garden. 



Select a plot of ground a few feet square, more or less, 

 free from rooted perennials, in which nature has sowed the 

 seed of annuals and where the seedlings are just beginning to 



