PRINCIPLES AND PRACTICE OF CLASSIFICATION. 79 
species; as, Turdus migratorius, for the robin. This is the ‘‘ binomial nomenclature” (badly so 
called, for ‘‘binominal” would be better); introduced by Linnzeus in the middle of the last cen- 
‘tury. It was a great improvement upon the former method of giving either single arbitrary names 
to birds, often a mere Latin translation of their vernacular nickname, or long descriptive names 
of several words; probably no other single improvement in a method of nomenclature ever did 
so much to make the technique of nomenclature systematic. To couple the two terms at all 
was a great thing, the convenience of which we who never felt its want can hardly appreciate. 
To follow the generic by the specific term was itself of the same advantage that it is to have 
the Smiths and Browns of a directory entered under S and B, instead of by Johns and Jameses; 
besides according with the genius of the Romance languages, which commonly put the adjec- 
tive after the noun. A Frenchman, for example, would say, Bec-croisé aux ailes blanches de 
VAmérique septentrionale, or ‘‘ Bill-crossed to the wings white of the America north,” where 
we should say, ‘‘ North American white-winged Cross-bill,” and Linnzus would have written 
Loxia leucoptera. The binomial scheme worked so well that it came to have the authority 
and force of a statute, which few subsequent naturalists have been inclined, and fewer have 
ventured, to violate; while it became an ex post facto law to prior naturalists, ruling them out 
of court altogether, as far as the legitimacy of any of the names they had bestowed was con- 
cerned. It necessarily rested, however, or at any rate proceeded upon, the false idea of a species 
asa fixity. Linneeus himself experienced the inadequacy of his system to deal binomially with 
those lesser groups than species, commonly called ‘ varieties,” now better designated as “‘ con- 
species” or ‘‘ subspecies”; and he often used a third word, separated however from the 
binomial name by intervention of the sign ‘‘ var.” or some other symbol. Thus, if he had 
supposed an American crossbill to be a variety of a European Lowia leucoptera, he might have 
called it Loxia leucoptera, a, americana. Some years ago, in treating of this subject, I urged 
the necessity of recognizing by name a great number of forms of our birds intermediate between 
nominal species, and connecting the latter by links so perfect, that our handling of ‘ species” 
required thorough reconsideration. The dilemma arose, through our very intimate knowl- 
edge of the climatic and geographical variation of “species,” either to diseard a great number 
that had been described, and so ignore all the ultimate modifications of our bird-forms; or else 
to recognize as good species the same large number of forms that we knew shaded into each 
so completely that no specific character could be assigned. In the original edition of the 
present work (1872), I compromised the matter by reducing to the rank of varieties the nominal 
species that were known or believed. to intergrade ; and the original edition of the ‘‘ Check 
List” (18738) distinguished such by the sign ‘‘ var.” intervening between the specific and the 
subspecific name. I subsequently determined to do away with the superfluous term ‘ var.,” and 
in the next edition of the Check List (1882) reverted to a purely trinomial system of naming 
the equivocal forms; as, Loxta curvirostra americana. The same system is used in the present 
treatise ; it is found to work well, and seems likely to come into general employ, at least in 
this country. It is commended to the consideration of our brethren over the sea. 
The Student cannot be too well assured, that no such things as species, in the old 
sense of the word, exist in nature, any more than have genera or families an actual existence. 
Indeed they cannot be, if there is any truth in the principles discussed in our earlier paragraphs. 
Species are simply ulterior modifications, which once were, if they be not still, inseparably 
linked together; and their nominal recognition is a pure convention, like that of a genus. 
More practically hinges upon the way we regard them than turns upon our establishment of 
higher groups, simply because upon the way we decide in this case depends the scientific 
labelling of specimens. If we are speaking of a robin, we do not ordinarily concern ourselves 
with the family or order it belongs to, but we do require a technical name for constant use. 
That name is compounded of its genus, species, and variety. No infallible rule can be laid 
