PRINCIPLES, CANONS, AND RECOMMENDATIONS. 31 



The rules for the practical handling of trinomials, being not different from 

 those for the use of binomials, will be given with the latter, beyond, under 

 the appropriate heading. 



A prevalent misapprehension respecting the meaning and office of the tri- 

 nomial system may be here corrected. Trinomials are not necessarily to be 

 used for those slightly distinct and scarcely stable forms which zoologists 

 are in the habit of calling * varieties ' ; still less for sports, hybrids, artificial 

 breeds, and the like ; nor indeed to signalize some grade or degree of differ- 

 ence which it may be desired to note by name, but which is not deemed 

 worthy of a specific designation. The system proceeds upon a sound scien- 

 tific principle, underlying one of the most important zoological problems of 

 the day, no less a problem than that of the variation of animals under 

 physical conditions of environment, and thus of the origin of species itself. 

 The system is also intimately connected with the whole subject of the geo- 

 graphical distribution of animals ; it being found, as a matter of experience, 

 that the trinomial system is particularly pertinent and applicable to those 

 geographical 'subspecies,' 'races.' or 'varieties,' which have become recog- 

 nizable as such through their modification according to latitude, longitude, 

 elevation, temperature, humidity, and other climatic conditions. Such local 

 forms are often extremely different from one another ; so different, in fact, 

 that, were they not known to blend on the confines of their respective areas, 

 they would commonly be rated as distinct species. This large and pecu- 

 liarly interesting class of cases seems not to have hitherto been adequately 

 provided for in the stringency of binomial nomenclature. 



It is obvious, therefore, that the kind or quality, not the degree or quan- 

 tity, of difference of one organism from another determines its fitness to be 

 named trinomially rather than binomially. A difference, however little, that 

 is reasonably constant, and therefore ' specific ' in a proper sense, may be 

 fully signalized by the binomial method. Another difference, however great 

 in its extreme manifestation, that is found to lessen and disappear when 

 specimens from large geographical areas, or from contiguous faunal regions, 

 are compared, is therefore not 'specific,' and therefore is to be provided for 

 by some other method than that which formally recognizes ' species ' as the 

 ultimate factors in zoological classification. In a word, intergradation is the 

 touchstone of trinomialism. 



It is also obvious, that, the larger the series of specimens handled, the more 

 likely is intergradation between forms supposed to be distinct to be estab- 

 lished, if it exists. This is perhaps one reason why trinomialism has been 

 so tardy in entering nomenclature. For until the animals of large areas be- 

 come well known, in all their phases, through extensive suites of specimens, 

 neither the necessity of trinomialism, nor the possibility of putting it to the 

 proper test, is apparent. It is gratifying evidence, therefore, of the progress 

 of Ornithology, and of the position attained by that branch of science in 

 America, that the members of an American Ornithological Association have 



