1SS4.I Corrispoiideiice. ■ 20I 



questions, of which some at least ol' tlic 'iml)elie\ers' have little concep- 

 tion — yet we can hardlj believe it unkind on our part to ask the 'unbe- 

 lievers' to answer for themselves the questions, whether expert testimony, 

 in mutters of science at large, or in human aftairs in general, is entitled to 

 an^- more weight than lay opinion ; or whether if they had had the same 

 o])])v)rlunities for stud\-, and the same amount of material for investiga- 

 tion, they bclic\e that they would have reached other than the same con- 

 <-lusit)ns, or would ha\e taken any dill'erent course of action. 



As to varieties and trimonials making nomenclature more complicated, 

 and the study of ornithology' more difiicult, is not the difliculty complained 

 of necessarily inherent in the subject, and dependent rather on the degree 

 of knowledge the student aspires to acquire, than on any needless en- 

 cumbrances thrown in the way by the 'leaders' in the science.'' 



But our correspondent will, we fear, think, in this instance at least, thr.t 

 our reply is not only ungracious, but that we are seeking to evade tlie 

 issue he presents. We must therefore say, that to discuss the subject in 

 its nian_y bearings, and in a way to present in argument what could be 

 quickly and easily shown by recourse to specimens, would require a long 

 essa\- rather than the few paragraphs here at command. So we must con- 

 tent ourselves with adding to what was said or implied in the reply to our 

 correspondent's former letter, and in Dr. Coues's letter above given, that 

 a philosophic principle underlies the whole subject, and that it is not 

 merely a matter to be decided by 'convenience.' While classification 

 is to some extent conventional, the object of classification in zoology is 

 to express the natural or genetic relationship of the objects classified; and 

 the proper distinction of varieties from species is by no means an 

 unimportant element in this scheme. The 'unbelievers' for whom Mr. 

 Chamberlain speaks are not to be presumed to be so skeptical as to ignore 

 the modern doctrine of evolution ; and, viewed from this standpoint, it 

 makes a vast difference whether we indifferently term a given form a 

 'species' or 'variety' in obedience to a mere principle of convenience. 

 As Dr. Coues above states, the recognition of a form as a species 

 implies "that the diff'erentiation is accomplished, the links are lost, and 

 the characters actually become 'specific' " By varieties are meant forms 

 that are not t\illy diflferentiated — in other words 'incipient species,' or 

 species still in the process of evolution. It hence follows that the terms 

 species and varieties are not interchangeable at will, but expressions for 

 certain definite and known facts in nature, grounded on a philosophic 

 principle, to ignore which is not only unscientific, but is to deprive us of 

 a means of precise definition at a point where precision is of high impor- 

 tance. As we said before, and as Dr. Coues i-estates. the determination 

 of how great a divergence from the. common stock a form must hlave to 

 render it desirable to recognize it in nomenclature, "is amatter of tact and 

 experience, like the appreciation of any other group in zoology.'' 



As is well known, no two individuals of any species are exacth- alike: 

 yet it would be absurd and useless, were it not also impossible, to giva 

 names to each. There are also manv local variations that are not too 



