I.] HEREDITY AK ACQUIRED CHARACTER. 23 



species, you will find the most persistent effort necessary 

 to prevent unlimited variation, * * * The difficulty is 

 not so much to secure a new variety or a new species as 

 it is to estaV)lish and confirm it." 



In other words, I look upon heredity as an acquired 

 character, the same as form or color or sensation is, and 

 not as an orij^inal endowment of matter. The hereditary 

 power did not originate until, for some reason, it was 

 necessary for a given character to reproduce itself, and 

 the longer aii}' form or character was perpetuated, the 

 stronger became the hereditary power. 



It is now pertinent to enquire what determined the 

 particular differences which we know to have persisted. 

 The mere statement that some forms became sessile or 

 attached to the earth, and that others became or re- 

 mained motile, is an assumption that these differences 

 were direct adaptations to environment. Everj- little 

 change in environment incited a corresponding change 

 in the plastic organization; and the greater and more 

 various the changes in the physical attributes of the 

 earth with the lapse of time, the greater became the 

 modifications in organisms. I believe, therefore, that 

 the grejiter part of present differences in organisms are 

 the result, directly and indirectly, of external stimuli, 

 until we come into those higher ranges of being in 

 which sensation and volition have developed, and in 

 which the effects of use and disuse and of psychological 

 states have become increasingly more important as fac- 

 tors of ascent. The whole moot question, then, as to 

 whether variations are definite or multifarious, is aside 

 from the issue. They are as definite as the changes in 

 the environment are, which determine and control their 

 existence. More differences arise than can persist, but 



