23 
THE LAW OF PRIORITY. 
Art. 25. The valid name of a genus or species can be only that name 
under which it was first designated on the condition: 
a. That this name was published and accompanied by an indication, 
or a definition, or a description; and 
~b. That the author has applied the principles of binar} T nomenclature. 
Discussion. — The law of priority is the keystone of nomenclature. 
Various attempts have been made to introduce substitutes for it, but 
none have succeeded. 
The point is not infrequently raised that not all zoologists favor this 
law. To this repty may be made that all persons who have studied 
the subject carefully see in this law the only hope for an international 
and stable nomenclature. It is especially the systematists, namely, the 
men who have to deal with tens of thousands of names, who have 
insisted upon its adoption; that some physiologists and morphologists 
(who have to deal with a few score, or a few hundred, at most a 
few thousand names) should oppose this law is not strange, for their 
field of study has not been in the line in which the necessity for the 
law lias come home to them. But we do not go to a gynecologist to 
obtain an opinion on the question whether we should wear glasses nor 
to an alienist in case we have appendicitis. By following the advice 
of the ophthalmologist in reference to our eyes, and of the surgeon 
in reference to appendicitis, we cast no reflections upon the ability of 
men in other specialities, but we go for advice to men who have had 
particular experience in the particular line in which we wish the 
advice. In nomenclatural matters, we naturally turn to the syste- 
matists, and they are practically unanimous in favor of the law of 
priority. In accordance with this law we do not inquire which of the 
110 or more names for the echinococcus worm is the most euphoneous, 
the most classical, the most generally used, the easiest to remember, 
the one of American or of Chinese origin; we simply inquire: Which 
is the oldest available generic name and the oldest specific name? A 
combination of these two gives us the correct binomial, regardless of 
our subjective views on the question. A few practical examples may 
be of interest in this connection. 
Tdenia was described in 1758, with four species, as follows: 
1. solium , which is now divided into 
(a) solium, for which about 90 names have been used; 
( b ) saginata, for which about 50 names have been used; 
(c) hydatigena, for which about 40 names have been used. 
2. vulgaris^ same as 3. 
3. lata, now Dibothriocephalus latus, for which about 30 names have been used. 
4. canina, now Dipylidium caninum , for which more than 15 names have been 
used. 
