222 PRIMARY FACTORS OF ORGANIC EVOLUTION. 



It has been proved, as it appears to me, that the vari- 

 ation which has resulted in evolution has not been 

 multifarious or promiscuous, but in definite directions. 

 It has been shown that phylogeny exhibits a progres- 

 sive advance along certain main lines, instead of hav- 

 ing been indefinite and multifarious in direction. 



It is not denied that many lines of variation have 

 been at one geologic period and another discontinued. 

 It is also true that certain divergences from the main 

 lines have appeared, and that minor and secondary 

 variations have occurred. Such variations do not seem 

 to have had any material effect on the general course 

 of evolution. In many cases such variations from 

 main lines might be compared to the undulations in 

 the course of a stream, which nevertheless seeks its 

 lowest level in spite of all temporary obstacles. Pro- 

 fessor Scott has termed these temporary variations "nu- 

 tations," in an able article on the subject. ^ "Sports" 

 seem to have been of no importance in evolution what- 

 ever. 



1 American Jottrnal Sci. Arts, Vol. XLVIII., 1894, p. 355. 



