8 Allen on the Recognition of Geographical Forms. [January 



are coming to light, often where least expected ; every consider- 

 able series of specimens from any locality previously known only 

 superficially presents us with, if not new nameable forms, at least 

 a new set of puzzling intergrades, tending to unsettle opinions we 

 thought were safely grounded, and showing that every question 

 touching the status of species and subspecies is still more or less 

 open to revision. 



Unquestionably the tendency at present is to name forms which 

 six years ago would have been considered too slightly differen- 

 tiated to require such recognition. On the other hand, differences 

 long since noticed, have but recently come to be properly under- 

 stood. In the light of new material they prove to have a signifi- 

 cance previously unappreciated, owing to the absence of the 

 requisite data. 



It is still evident, however, that great caution should be exer- 

 cised in bestowing trinomials, in order to guard against drawing 

 too fine distinctions. Very little is gained by naming races dis- 

 tinguishable only by expeits, aided by a large amount of material, 

 or where the differentiation is largely a matter of a slight average 

 difference between forms contiguous in habitat — forms which nine 

 out of ten ornithologists of average acuteness and experience, and 

 with only ordinary resources, will be more or less unable to satis- 

 factorily distinguish. In fact, a form based on a certain series of 

 specimens may seem to any investigator of this same material 

 well founded, but when judged by other material not unfrequent- 

 ly loses much of the distinctness it seemed to present when 

 tested by the first set of specimens. 



There are necessarilv, in cases of wide-ranging species which 

 run into well-marked geographical forms, numerous connectent 

 series, made up of intergrades of all degrees of relationship to the 

 more extreme phases. Some of these intergrades may seem dif- 

 ferent enough from either extreme to warrant recognition as an 

 additional subspecies. By such a course what do we gain? 

 We bridge the difficulty by doubling it ; we get rid of one set of 

 of troublesome intergrades by creating two others ; leading the 

 way to further subdivision of like character, and increasing the 

 difficulties. Obviously the situation is not in this way improved. 

 Yet the tendency to this sort of division is evidently increasing, 

 each step in this direction making the next one easier. Only the 

 exercis^ of due discretion can prevent the reduction of "our bene- 



