572 THE AMERICAN NATURALIST [Vol.L 



have similarly bright and striking plumage, especially in 

 the males, though the sitting females may be dull. The 

 bright colors of the males may readily have been ac- 

 quired under control of similar forces. I do not mean 

 to rob sexual selection of its reputed force, but indica- 

 tions are that it is not entirely responsible for all that 

 might be laid to its door. The genus Dendroica of small 

 active arboreal birds has developed numerous bright, 

 varied and beautiful colors. Two species perhaps as 

 closely allied as any others are the Blackpoll Dendroica 

 striata and Bay-breasted warblers, Dendroica castanea. 

 It is interesting to find them very fair complements, the 

 one of the other, in plumage of the breeding male, though 

 females and young are little different ; whereas the male 

 blackpoll resembles in color the black and white warbler, 

 MniotUta varia, a distantly related bird of the same 

 family. 



Ten years ago the writer had the pleasure of making 

 the acquaintance of the beautiful grey slender-billed 

 fulmar (Priocella), on the southern ocean. Sometime 

 afterwards when crossing the North Atlantic he met with 

 the northern fulmar (Fulmarus) and was surprised to find 

 the resemblance between the two so great, even carried 

 to a light mark on the wing, very useful in field iden- 

 tifications. Though belonging to the same family the 

 two species are really not very closely allied and are an 

 example of the outcrop. Another case which might be 

 so considered is that of the African true larks or pippits 

 which simulate our meadow larks of the family Icteridse 

 in color. All passerine birds are so closely allied that 

 the two are not too distantly related to be outcrops, but 

 there are other reasons for thinking that this case is not 

 a very good one, but rather a case of environmental 

 parallelism. The black breast mark, for instance, is so 

 common among ground birds that it probably has con- 

 cealing value. 



The isolated islet of South Trinidad in the south At- 

 lantic is remarkable in that three closely related species 



