IQo Com'spondeiice. (April 



a formulation of the principle upon which 'the American school' acts in 

 applying this method of nomenclature. The following paragraph is taken 

 from a plate-proof of my new 'Key,' p. 76, long since stereotyped, but 

 not yet published : — 



"No infallible rule can be laid down for determining what shall be held 

 to be a species, what a conspecies, subspecies, or variety. It is a matter 

 of tact and experience, like the appreciation of the value of any other 

 group in zoology. There is, however, a convention upon the subject, 

 which the present workers in ornithology in this country find available ; 

 at any rate, we have no better rule to go by. We treat as 'specific' any 

 form, however little different from the next, that we do not know or 

 believe to intergrade with that next one; between which and the next one 

 no intermediate equivocal specimens are forthcoming, and none, conse- 

 quently, are supposed to exist. This is to imply that the differentiation 

 is accomplished, the links are lost, and the characters actually become 

 'specific' We treat as 'varietal' of each other any forms, however differ- 

 ent in their extreme manifestation, which we know to intei-grade, having 

 the intermediate specimens before us, or which we believe with any good 

 reason do intergrade. If the links still exist, the differentiation is still 

 incomplete, and the characters are not specific, but only varietal, in the 

 literal sense of these terms. In the latter case, the oldest name is re- 

 tained as the specific one, and to it is appended the varietal designation : 

 as. Tardus migratorhis fro-pmqutts.^' 



While it is always safer to prophesy after than before the event, I 

 nevertheless venture to predict that the nomenclature of the near future 

 will fully recognize some such principle as this, and apply it by means of 

 trinomial nomenclature, in Em-ope as well as in America, and especially 

 in Great Britain. In my judgment, the interests of the B. O. U. and of 

 the A. O. U. would both be subserved by an alliance in this particular. 



Very truly yours, 



Washington, February 20, 1884. Elliott Coues. 



Are Trinomials Necessary ? 



To THE Editors of The Auk :— 



Sirs: I feel sure that every amateur who has read the reply to my 

 letter in the January number of this magazine will feel as sincerely thank- 

 ful for it as I certainly do — grateful for the information conveyed, 

 and pleased to have the proof that such questions as I have asked will 

 receive kind and courteous consideration in the pages of 'The Auk.' 



Candor compels me to add, however, that the reply has not, in some 

 points at least, proved entirely convincing, and I return' to the subject for 

 the purpose of gaining further light. 



It is to be hoped that the more advanced students will not grow impa- 

 tient over the persistency and, perhaps to them, apparent stupidity of 

 these unbelievers of the 'amateur element.' Those who have passed 

 from unbelief to a firm conviction that trinomials are useful and neces- 



