The Evolution of Organisms 169 



animate world. Here the general trend of things has 

 been progressive. liow important if we can spell 

 out the mechanism of progress ! In this connection 

 we venture to submit some general considerations. 



A Common Error as to Fortuitousness. — Many have 

 recoiled from a theory of evolution which seemed 

 to rely so much on happy chances and on the oc- 

 casionally apt ending of a chapter of accidents. 

 What have we to say to this ? 



It is in part a misunderstanding of words. 

 When an evolutionist speaks of "fortuitous varia- 

 tions," he means that he is ignorant of their ante- 

 cedent conditions. Fluctuating variations can be 

 arranged so as to form a curve — the curve of the 

 frequency of error — the curve which we get when 

 we plot out measured results depending on a num- 

 ber of variable conditions. But the mere fact that 

 we can make the curve shows a certain orderliness 

 of distribution. Chance is a most orderly phe- 

 nomenon. Furthermore, there is often marked 

 definiteness in continuous variation, it accumulates 

 generation after generation, one organ increases, 

 another dwindles. Furthermore, it is by no 

 means certain that any big step has been made by 

 the accumulation of minute fluctuations; it is prob- 

 able that discontinuous variations or mutations 

 have counted for much, and they are no more ac- 

 cidental than sudden growth is. Furthermore, 

 while there have been catastrophes in the course of 



