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merits, and that these elements are associated in groups ;. the same 

 elements or groups of elements may, and supposedly do, recur in 

 related species. The origin of a species by mutation would im- 

 ply the substitution of a new elementary character, or quality, in 

 the combinations, or groups, much after the same manner in 

 which changes in the constitution of chemical bodies are effected. 



It is these elementary units or characters which must be con- 

 sidered in the analysis of the qualities of a hybrid, and the proper 

 application of the principles involved will, as de Vries asserts, 

 afford an adequate explanation of the composite nature of hy- 

 brids. The forthcoming volume of this author upon the subject 

 will be awaited with the greatest interest by all concerned with 

 questions of descent and heredity. 



From the reviews and discussions which have already been 

 made of de Vries' papers it is to be seen that the greatest misun- 

 derstanding which may likely arise in the consideration of his 

 results will be that founded on the error of confusing fluctuating 

 variability and mutability. Individual variations, or fluctuating 

 variations, may be caused by altered conditions of nutrition or 

 other environmental factors, and when these conditions are ap- 

 plied and directed in gardening and agricultural operations they 

 may give rise to the so-called improved races. Such variations are 

 exhibited constantly, and in great number, and soon reach a 

 maximum limit in any given direction, or in the development of 

 any single quality, usually within a few generations, and the total 

 departure from the original type is never sufficient to constitute 

 an independent species, or true variety. Mutability on the other 

 hand is a variation implying, and due to, the appearance of new 

 qualities, or the disappearance of existing characters, or the rear- 

 rangement of elements, in such manner as to constitute new char- 

 acters. Mutations are enormously rare in comparison with the 

 fluctuating variations described above, and this very rarity has led 

 to an underestimation of their value in the origin and develop- 

 ment of species, according to de Vries' conclusions. 



The writer is aware that the foregoing statements may be taken 

 as a somewhat bold setting forth of the mutation theory, but still 

 it is believed that the main contentions of de Vries are rightly 



