10 VARIATION 



He cannot know too much about life and its vicissitudes, about 

 living things and what they do. 



An animal is born into the world. Its energies are first 

 devoted to nutrition and growth. It builds its own machine 

 and builds it quickly out of materials lying close at hand. In 

 good time it is finished and all its energies are at a maximum. 

 It seems like a stable thing that must live forever. But repro- 

 duction occurs, securing a succession of its kind. One after 

 another of its faculties fail, and its condition is again reduced to 

 that of bare existence, with youthful recuperative powers gone 

 forever. By and by some vital function fails. Then life goes 

 out ; the organism breaks down and returns its elements to the 

 inorganic world. Such is the brief history of a bit of matter 

 temporarily endowed with life, fleeting as a breath; any 

 service it may render us must be caught in the passing. 



SECTION III NATURE OF VARIABILITY 



The exact nature of variability is a most obscure subject, 

 and one that cannot be fully comprehended in the present 

 state of knowledge. Whether the distinctions between living 

 and non-living matter will always remain as marked as they 

 now seem to be, only future discoveries will determine. We 

 have as yet only touched the fringe of this great subject, but 

 enough is known to enable us to begin to penetrate some of its 

 mysteries. 



At least two general principles may be laid down in the 

 present state of knowledge without much chance of error : 



1. That all characters of plant and animal life, whether struc- 

 tural or functional, are exceedingly variable. 



2. That ordinary variation is the result of a change in the 

 relations between a number of associated characters through the 

 deviation of one or more of the members, and not the introduc- 

 tion of an absolutely new character. 



We speak loosely of " introducing new characters," but in 

 truth improvement consists, not in the introduction of absolutely 

 new characters, but in the intensifying of desirable old ones and 

 the subordination of those that are undesirable. For example, 



