The Factors of Evolution 243 



smaller curves be compounded they produce the large curve 

 representing the larger group. In some instances the 

 existence of several modes is seen in the original chart of a 

 group of organisms. In other cases however mere inspection 

 fails to reveal the compound nature of a variability curve, and 

 only experimental analysis will tell the story. 



These minor groups which when selected breed true to their 

 own type, are the ''elementary species" of DeVries, or dis- 

 continuous variations, while the ''fluctuating variations " are 

 those which fluctuate about a mode and which cannot be re- 

 solved into smaller components by selection. From this view- 

 point "species" and "elementary species' may be compared 

 in a rough way to the molecule and atom of the chemist. 



The objection has been raised to DeVries' theory that his 

 mutations are the results of hybridization, producing a new 

 combination of characters already present, but not anything 

 really new in itself. The wide range of mutation however 

 among both plants and animals, wild as well as domesticated, 

 from the large "sports" of Darwin down to those so small 

 that they cannot be distinguished at sight from "fluctuat- 

 ing" variations, the fact that in some species there are peri- 

 ods of frequent mutation, , alternating with those in which 

 it is absent or rarer, and the possibility of inducing them 

 artificially all speak in their favor as something new, and 

 not due to a mere mixing and rearrangement of characters 

 already present. Unless indeed we accept Bateson's view 

 that most if not all variation is due to the loss of something 

 already present, which, carried to its logical conclusion, 

 brings us face to face with the reductio ad absurdum that 

 all the possibilities of man were wrapped up in the original 

 Amoeba, or whatever it was that initiated the long line of life 

 upon the earth. 



But having analyzed the species into its component parts, 

 having found the blocks from which the organism is built, 

 are we any the wiser? Whence came these ultimate units, 

 if indeed they are such, and how does Nature fashion them 

 to her use? Are we any nearer an understanding of varia- 

 tion today than was Darwin? 



The attack on the problem of variation has been made 

 along two distinct lines, that of Aristotle and Nageli, with the 

 assumption of an "internal perfecting principle," or in- 

 herent tendency in the organism itself to vary along certain 

 definite lines, for unknown reasons, and that of Eimer and 

 his school, who believe that variation in the organism is a 

 very definite physico-chemical response to physico-chemical 



