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THE AMERICAN NATURALIST [Vol. XLII 



recognized by a more or less careful examination of a 

 single individual of unknown ancestry. To the experi- 

 mentalist, whether he be a physiologist, an experimental 

 morphologist or a pedigree culturist, such a conception 

 of species makes them of no utility, and this is also 

 largely true with students of cytology, anatomy, etc., who 

 study the morphology of structures not externally visible. 

 As a student of variation and heredity from the experi- 

 mental side, I hold that the natural group is the only one 

 that can be of any utility to any one but the herborizer, 

 but I do not insist on the privilege of calling this natural 

 group a species. That matter is entirely immaterial. 

 To avoid confusion, we are now calling these groups 

 elementary forms, but this expression is unnecessarily 

 cumbersome for the constant use the conception must have 

 in the future literature of botany, and I hope that some 

 one will come forward with an acceptable short designa- 

 tion for these, in case the herborizer succeeds in checking 

 the trend of development of the conception of species 

 from an arbitrary to a natural one. 



Experimental evidence at the present time shows at 

 least two grades of form-groups. These were recognized 

 by Dr. De Vries under the names, elementary species 

 and varieties. By "varieties" De Vries indicates those 

 forms which differ from their nearest related form in 

 one or more characteristics, which behave according to 

 Mendel's law upon crossing with it. As taxonomists 

 have definitely abandoned the use of the term "variety" 

 to the horticulturist, we need a new word with which to 

 speak of this very definite class of forms. As we have 

 taken liberties with the name of Mendel in the formation 

 not only of the adjective "Mendelian," but also the verb 

 "Mendelize," there seems to be no reason why we might 

 not go farther and call these Mendel ian varieties Mendel- 

 ities. These Mendelities are hangers-on of species, and 

 corresponding Mendelities may belong to many different 

 species, as may be illustrated by the frequency of occur- 

 rence of white-flowered or albino forms, which differ 



