222 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
The geneticist has a peculiar interest in species and has always dealt 
with problems which have to do with' the real inwardness of the species 
concept. Biological philosophers have often given genetical definitions of 
the species concept, as did the “Father of Botany” himself in a certain 
limited sense when he assumed that there are “as many species as the 
Infinite Being originally produced different forms.” 
The first great geneticist, J. G. Koelreuter, devoted a great deal of 
attention to an attempt to determine whether certain putative species were 
in reality specifically distinct or only varietally, basing his conclusions on 
the degree of sterility or fertility of the two forms under test, when bred 
together, and upon the fertility or sterility of the hybrids produced by 
such cross-breeding. 
Not only this capacity for normal interbreeding, but also the degree of 
variability which occurs within normally interbreeding groups, have served 
as useful genetical characteristics of specific delimitation; but the usefulness 
of these phenomena as aids in determining what groups to call species is 
greatly lessened by the facts that so many species do not normally interbreed, 
and that not a few can not interbreed, as, for example, the parthenogenetic 
species of Taraxacum, Antennaria, etc. 
These facts make it necessary, in the use of such a criterion of species, 
merely to estimate the amount of variation which might he expected to occur 
normally within a freely interbreeding group; and when we must resort to 
this sort of abstraction, the method at once loses its value in relation to 
the discovery of natural limitations of species. The fact is that, although 
genetical phenomena form the basis of nearly all biological classification, 
there is no genetical criterion— nor any other criterion —of specific difference, 
which is found generally applicable or generally acceptable. The geneticist 
comes more and more to the point of view that the distinctions between 
species are only quasi-natural, that specific differences are by no means 
quantitatively equivalent in different genera, families, orders, or phyla, but 
that genetically there are very many different grades of distinction between 
the form-groups which are, with more or less justification, recognized by 
taxonomists as “species.” 
This being the case, it seems proper to insist .that utilitarian principles 
should be crucial in the establishment of new species and the maintenance 
of old ones. When we consider the whole question from the standpoint 
of convenience, it is clear that the needs and experiences of the user must 
be determinative. 
To the systematist, whether professional or amateur, the species classi¬ 
fication is the “bread of life”; but to other classes of biologists the species 
is merely a tool, handy or unhandy according as the taxonomist has done 
his work wisely or unwisely. To these other classes of biologists the species 
exist for the biologist, not the biologist for the species. Hence it often 
happens that the physiologist, the ecologist, the geneticist, etc., take 
