236 BULLETIN OF THE 



to A. Gambeli (= A albifrons ?), and the Anser cceruhscens to the A. 

 hyperboreus, though by some the former has been regarded as the young 

 of the later. In Larus argentatus the southern specimens are not only 

 smaller, with the " mantle " somewhat darker, but as a general rule the 

 white spots at the tips of the first and second primary quills are more 

 restricted. 



The changing of the pelage to white in winter in certain northern 

 mammals, and of the plumage in certain birds, as the ptarmigans, cor- 

 relates perfectly with these geographical differences in color; and since 

 in some species of mammals only the northern representatives change 

 to white in winter, while the southern ones are of the same color 

 throughout the year, this seasonal change seems evidently to come 

 under the above-stated general law of geographical or climatic color 

 variation, namely, a gradual increase in color to the southward in 

 individuals of the same species. 



A comparison of Florida birds with "West India specimens of the 

 same species shows that the difference between them in color (and, it 

 may be added, in size and other general features) are generally not 

 greater, and in some cases jfar less, especially between Cape Florida and 

 Cuba specimens, than obtains between Florida and Massachusetts 

 examples, and that it is of precisely the same character. West Indian 

 specimens of course differ more from Massachusetts examples of the 

 same species than the latter do from others from East Florida, yet by 

 means of the South Florida specimens, which differ but slightly from 

 the Cuba type, a gradual transition is evident from the extreme northern 

 to the extreme southern forms. Of late many Jamaican, Porto Rican, 

 and Cuban forms have been regarded, by many writers, as specifically 

 distinct from their representatives in the Northern States, and in many 

 cases they might well be so regarded, were there not a succession of 

 intermediate forms connecting them, — a fact which seems to have 

 been hitherto overlooked. The earlier writers considered the Ortyx, 

 the Slurnella, the Strix, the Circus, several of the Buteos, etc., of the 

 West Indies as specifically identical with the Ortyx virginianus, 

 Sturnella ludoviciana, Strix Jlammea, Circus hudsoniiis, Bntco bore- 

 alis, etc., of the United States, and doubtless justly, notwithstanding 

 that the comparison of specimens reveals certain relatively slight 

 but constant differences in color and size, and to some extent in 

 other features. 



