THE ADDRESS OF THE PRESIDENT 
THE TAXONOMIC UNIT 
T. C. STEPHENS 
The retiring president is expected to follow the custom of ad- 
dressing the Academy upon some subject of general interest. 
Fortunately, custom does not require that such an address 
shall embody one’s own research or investigation; but it may 
consist of a survey, or of reflections of a general nature. 
It so happens that certain fields in which I have been some- 
what interested have brought me to a study of the problem of 
the taxonomic unit in biology. 
One difficulty which concerns many working biologists, and 
which seems to be becoming more and more acute, is the determi- 
nation of the living forms upon which they work. 
Insofar as zoological and botanical work is to have a perma- 
nent value in science it must at all times be open to verification ; 
and it must at all times be possible to relate observations pre- 
cisely to the natural forms upon which they were made. The 
necessity of stability in nomenclature is obvious to all. 
Our studies in nature have proceeded so far, and differentia- 
tions are becoming so refined, that the problem of nomenclatural 
stability is becoming one of concern. In fact, there may be no 
such thing as stability; in which case the problem would be to 
build up a system that would cause the least amount of confusion 
in its operation. 
The ‘‘species question” is not new to you; and to most of you 
who are concerned with the biological field, at least, the tenden- 
cies are familiar. I have been loath to present to you a discussion 
of the species question, partly because of its venerable theme, 
and partly because it has received the attention of some of the 
most illustrious biologists, both of the past and of the present. 
In fact, I think it was Darwin who exclaimed “How painfully 
true it is that no one has the right to examine the question of 
species who has not minutely described many.” With this warn- 
ing a wiser soul might hesitate to proceed further. And yet, 
the subject is one that cannot be evaded, and is one which cannot 
be solved for us by the science of any previous period. 
