238 Heredity and Eugenics 



tions we have no means of knowing until more is known of 

 germinal constitution. It is clear, however, that by hybridi- 

 zation it is possible to bring about permanent modifications 

 of pattern, and these are not only modifications of color 

 pattern but also of the pattern of the structures, as for 

 example, the punctations, venation, etc. These latter 

 attributes are, by systematists, considered as characters 

 of prime importance, and are made the basis of innumerable 

 systematic distinctions, but in these experiments they 

 are as susceptible to changes, derangement, and de novo 

 variations as are the characters which are based upon color, 

 and color arrangement. In our present ignorance of the 

 nature of the localizing process in any material, either living 

 or non-living, we are left entirely in the dark as to what 

 actually goes on. The experiments, however, suggest the 

 manner in which modifications may result, and these 

 resulting modifications may well be productive of evolu- 

 tion changes either of advancement or regression. 



4. BY SELECTION 



DeVries correctly maintains that the quantitative 

 accumulation of small variations will be productive of a 

 modification which will move rapidly in a given direction 

 until the limit is reached. This can be demonstrated in 

 many plants and animals for a number of characters. The 

 manner in which quantitative accumulation operates is 

 well shown by the following examples: 



I attempted by selection to create an albinic race of L. decemlineata 

 in two ways — first, by selecting for breeding the most extreme albinic 

 variations found in nature, and second, by creating extreme albinic con- 

 ditions in experiment and breeding from them. For the first set 

 of experiments the selection was made from numbers of copulating 



