﻿38 FIELD AND FOREST. 



ticular species, are the main ground of the objections referred to, Mr. 

 Allen's attention having been called to the matter, as he states, by 

 communications from Captain Charles Bendireand Lieutenant George 

 R. Bacon, U. S. A., who, being stationed at a favorable locality had 

 excellent opportunity to study the two forms of L. tephrocotis — the 

 typical form and "var." littoralis—in the field, during their winter 

 hegira southward. The " very positive remarks " in question, were, 

 however, strictly the expression of the facts which suggested them, 

 verified by the field-work of naturalists to whose experience and ve- 

 racity as great respect is due as to Mr. Allen's correspondents — a consid- 

 tion I am sorry to see ignored in Mr. Allen's statement with reference to 

 the measurements appended to his article, to the effect that as they 

 " were made by the collector from fresh specimens, and as the sex of 

 each specimen was determined by actual dissection, they are of special 

 interest in the present connection." 



The point at issue is, whether the sexes of " tephrocotis " and " litto- 

 ralis' 1 ' 1 do, or do not, differ in plumage — which, in a diagnostic sense, 

 means whether thereare, orare not, absolutely co7istantsexud\ differences. 

 On page 60 of my monograph, under the head of " Sexual differences,' \ 

 I state: "The American species of this genus fall into two distinct 

 groups, according as the sexes do or do not differ in appearance. In 

 L. tephrocotis, in all its forms, there is not the slightest sexual differ- 

 ence ; but in L. atrata and L. australis, the distinction is very marked. 

 As a rule, the female is very slightly smaller than the male, but that she 

 is not constantly so is clearly shown by the following averages of large 

 series of each form." 2 Speaking of typical tephrocotis, on page 72, 

 I again remark: "The spring plumage of this race is represented in 



the series before me by thirty-five individuals, which show that there i 



. s 



able, test of whether differentiations noted in a form require " varietal" or " specific'' 

 recognition, the question of whether "connecting links" door do not occur, it is 

 found that such intergradation exists at present between only two of the five forms of 

 this genus, so far as known. This circumstance, then, entitles each of these forms to 

 specific rank, for, whatever may have been the period of their gradual differentiation they 

 have now passed the " varietal stage," through the final obliteration of all specimens of 

 intermediate characters. The two forms, whose "connecting links" have not thus been 

 destroyed, afford, however, the required evidence of a probably more recent common 

 origin, and may thus very properly be reduced to the rank of representative, or geo- 

 graphical races. Preference is in this case given the term geographical, from the 

 reason that whatever may have been the cause of the differentiation of the two repre- 

 sentative forms, it is evident that no explanation is afforded by " laws" based only 

 on present climatic conditions. 



