1896.] NATURAL SCIENCES OF PHILADELPHIA. 125 



almost entirely from the water birds, and we are not informed of the 

 exact character of the material which came under his observation, 

 all that we have is his interpretation of the facts. The species to 

 which he calls especial attention are the Dunlin, Knot and Sander- 

 ling. 



" In the Dunlin " he says " the change of colour develops itself 

 in the following manner : In the ash-grey feathers of the back the 

 shaft first becomes black ; this color spreads rapidly over the feath- 

 ers, finally leaving only broad gray margins. The latter at first 

 change to a dull rusty-grey, which, however, subsequently passes 

 into a beautiful ferruginous color. At the same time the dull ash- 

 grey tips of the feathers pass into a whitish-grey, their margins being 

 simultaneously rounded off to their former entirety." 



How such a theory could have been advocated, after the examina- 

 tion of a large series of specimens, I cannot understand, for a series of 

 spring examples of the American Dunlin taken on the coast of New 

 Jersey show the black and rusty feathers coming in abundantly and 

 supplanting the worn gray feathers of the winter plumage.'" 



In the Sanderling Giitke states there is a change from a uniform 

 light gray to a deep black, and from a beautiful ferruginous color 

 to a pure white. Here again spring specimens, from the coast of 

 New Jersey and Florida, show the black and ferruginous plumage 

 molting in and superceding the light gray plumage of winter. 



Gatke says (p. 163) that he " confines his description to what 

 actually takes place, without embarking on any hypothetical con- 

 jectures." In this, however, I cannot agree with him ; lie does not 

 claim to have seen the change in color actually take place in any 

 individual feather, and to make the assertion that feathers change 

 from one style of coloration to another when the only facts before 

 him are that he has feathers which represent those styles of coloration, 

 one of which might change to the other, involves entirely too great 

 an assumption. 



In his chapter on "colour-change without moulting" Gatke sup- 

 ports another theory, also originally advanced by Schlegel, but which 



'^ Since the present paper was presented to the Academy for publication (see 

 Proc. Acad. Nat. Sci. Phila., 1896, p. 12), Mr. F. M. Chapman has published 

 an article on " The Changes of Plumage in the Dunlin and Sanderling" (Bull. 

 Amer. Mus. Nat. Hist., VIII, p- 1—8), in which he criticises Griitke's state- 

 ments on the same grounds as above. Here again, it is interesting to note 

 that Mr. Chapman and the writer working independently, arrived at exactly 

 the same conclusions. 



