'I'l A. Correspondence. I Oct. 



Oriole is erroneous. He does not state why, as he says, "it is evident 

 that this mottled phase of plumage, occurring in a very large number of 

 species, is a permanent one for the time being . . . ," but remarks that 

 the assertion of a transition plumage "must be based on observation of 

 the living bird for a sufficient period to determine the nature of the change 

 of color." If this be so, then how can he so positively assert that the 

 color does not change in the young Oriole? Has he observed this in the 

 living bird? If so, he has forgotten to mention the fact, but if not, 

 his own conclusion is of no more value than mine, according to the 

 requirements he has himself made. However, as far back as 1S35, as 

 is noted in my paper, Yarrell recorded experiments of the sort demanded 

 by Mr. Allen, to prove that in certain species there is a change in color 

 without moult, viz., by marking feathers on living birds and observing 

 the change. Mr. Witmer Stone writes me on this subject as follows: 

 "1 have been paving especial attention to young birds in first plumage 

 during the past year, and while I cannot agree with Yarrell's idea of 

 the plumage changing without moult as a general rule, I think that in some 

 instances it is correct. In Icterus spurius, for instance, I cannot detect any 

 moult from the first plumage to the fall dress of the 'bird of the year,' 

 but there seems to be a darkening or intensification of the pigment." 

 Dr. C. Hart Merriam and Dr. L. Stejneger have both asserted that in 

 certain species a pigment change without moult occurs, and even if the 

 old experiment of Yarrell, when applied to Orioles, should prove my 

 deduction to be incorrect, it would not invalidate the assertion that in 

 certain exceptional instances there is a change of color without moult. [3] 



Concerning the mode of pigmentation of a feather, I would say that 

 although in the text of my paper I have neglected to allude to the embry- 

 onic development of a feather, I am of course aware that the pigment is 

 deposited during the process of formation of the feather. I am acquainted 

 with what Burmeister, Owen, Wiedersheim, and others say about feather 

 growth, but find nothing in their accounts to invalidate the position taken 

 in inv paper — viz., that the pigment is deposited along the lines of greatest 

 and least resistance. Burmeister does not even allude to detecting pigment 

 cells until the feather has attained a tolerably advanced stage of develop- 

 ment. He says: "But, if the feather be colored, an accumulation of pig- 

 ment is formed on each of the oblique striae above each of its individual cells, 

 and this is larger the nearer the cell is to the main stem of the barb." 1 This 

 remark with others of a like nature would rather strengthen than detract 

 from my contention that pigment deposition is in accordance with Prof. 

 Cope's law of growth force. 



The remarks upon hybrid feathers which Mr. Allen calls "the various 

 classifications and generalizations based on this erroneous departure," are 

 quite independent of the theory intended to account for them. It is merely 

 an attempt to classify certain facts, which, so far as I can discover, have 

 been previously ignored, — viz., the plan of coloration of individual feathers 



1 Nitzsch's Pterylography, p. 8. 



