488 Recent Literature. [o"t. 



such a problem by mathematical rules or with mathematical accuracy 

 because systematic zoology is of necessity not an exact science. 



To take an example from another group we wonder how Dr. Dwight 

 would arrange the smaller Thrushes according to the criteria which he has 

 laid down. Could not the differences between the Olive-backed and Gray- 

 cheeked Thrushes be regarded as quantitative or qualitative according to 

 the viewpoint of the individual? As a matter of fact the Gray-cheek was 

 regarded as a subspecies of the Olive-back until it was found that forms 

 of the two bred side by side without intergradation. In this connection 

 it is interesting to note Dr. Frank M. Chapman's method of handling the 

 subspecies problem in his recent work on the birds of Colombia. He 

 says; " To lay down a certain rule and blindly be governed by it, is to 



handicap one's discrimination and experience The degree, and 



particularly the character of the differences exhibited, range, environ- 

 ment, faunal areas, the relative plasticity of the species in question, the 

 action of other organisms in the regions concerned under similar circum- 

 stances, these and other factors, such as habits, voice etc., are to be con- 

 sidered in reaching a conclusion regarding the status of any form." 



In this discussion we would not be understood as reflecting upon the 

 excellent work that Dr. Dwight has done on the Juncos with the results of 

 which we are in substantial accord. Furthermore we have always believed 

 (cf . The Condor, March, 1903) that a plan might be devised — an arbitrary 

 consensus of opinion if need be — by which a long series of races widely 

 divergent at the extremes of the series but all apparently intergrading, 

 could be broken up into specific groups, while forms widely separated 

 geographically but differing very slightly from one another could be re- 

 garded as subspecies. A happy compromise as it were between the ' degree 

 of difference ' principle and that of ' geographic intergradation ' which 

 would vastly enhance the meaning which our names are supposed to convey. 

 This is apparently just what Dr. Dwight is striving for but that any set of 

 rules can be laid down by which anyone may determine the proper rank of 

 a given form seems from the very nature of the case impossible. 



One point that Dr. Dwight brings up in connection with his discussion 

 of the race of J unco oreganus deserves special consideration. At a single 

 locality within the range of J. o. thurberi he finds some breeding specimens 

 which would on color alone be better referred to J . o. oregonus and J. o. 

 couesi and he contends that if we are naming the birds and not the locality, 

 these specimens should bear the names of these races rather than that of 

 the race to which the vast majority of the individuals at that locality belong. 

 Here our author is disregarding everything but color. It is a foregone 

 conclusion that all the breeding birds at this locality belong to the same 

 stock and should bear the same name with a comment if need be on 

 aberrant characters. They are simply evidence of that intergradation of 

 the three forms which shows them to be subspecies. This intergradation 

 may be found in the area where the breeding ranges join, in which case it 

 is manifest in a majority of the individuals, or it may be found in a large 



