THE SPECIES CONCEPT FROM THE POINT OF VIEW 
OF A MORPHOLOGIST 1 
R. A. Harper 
On the reality of organic evolution we all agree; but has the species 
concept outlived its usefulness? It served prior to Darwin as an expression 
of the dogma of special creation. Does it serve equally well now to represent 
concrete realities as seen from the evolutionary standpoint? Morphology 
is essentially a comparative science dealing with phylogenies, and the 
limiting of this paper to the twenty minutes allowed will permit only of a 
resume rather than of the presentation of the detailed data as to the true 
significance of the species concept as related to phylogeny and evolution. 
On the matter of species it is to be noted that Darwinian evolution dealt 
rather with the question of origins than with that of content. In' this 
particular the change is not per se so basic as we sometimes think. Linnaeus’ 
idea of a species as a recognizably distinct group of interbreeding individuals 
all having a common descent is still the basis of most of our clear thinking 
in matters of classification. The evolutionary dictum that species originate 
as variants from a parent group and are themselves the potential parents 
of groups yet to be produced does not necessarily affect the question as to 
their make-up or delimitations at any given time. 
Does the concept species represent as adequately the unit of evolutionary 
progress as it did the unit for theories of special creation? The value of 
a scientific concept is not infrequently in direct proportion to its plasticity 
as shown in its ability to undergo more or less fundamental and far-reaching 
changes in its significance with the increase of our knowledge of the subject 
data on which it is based. For example, in cytology the concept cell has 
shown its utility by surviving such fundamental modifications in content 
as are involved in the change from its original use as relating to a cavity 
or box-like chamber in plant tissue to its present use to designate a one- or 
several-nucleated mass of protoplasm. The changes now going on in the 
conceptions back of the term atom are another illustration in point. 
I suppose there never was a time before in the history of science when 
a theory played such a dominant role as has the theory of evolution since 
the time of Darwin. Never has a viewpoint proved so fruitful of new 
interpretations, so stimulative of productive research. Its basic concepts 
dominate alike morphology, physiology, sociology, and such less sharply 
defined realms as psychology and philosophy. The only comparable case 
1 Read in the symposium on “The Utility of the Species Concept,’’ at the joint meeting 
of Section G of the American Association for the Advancement of Science, the American 
Phytopathological Society, and the Botanical Society of America, at Toronto, December 
28, 1921. 
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