60 Stray Feathers. [isfj'uly 



deals with the various theories put forward, and shows where 

 they fail. Starting with the assumption that a solution of the 

 problem (change of colour without moult) " could not be attained 

 without a thorough consideration of the cause of colour and 

 its development," he arrives at the conclusions that — " The 

 contention for a flow of pigment from the barbs into the 

 barbules, &c. . . . is at once made absurd by the fact that 

 the barbules are pigmented before the barbs are differentiated. 

 Variations in colour patterns are usually correlated with 

 variations in the distribution of pigment in the earlier stages 

 of the feather's development. When completed the feather is 

 composed of cells which have dee// entirely metamorphosed into 

 a firm horny substance, and its pigment is imbedded in that 

 lifeless matter. The cells composing a barbule are fused into a 

 solid, more or less homogeneous structure. The pigment of 

 one portion of the barbule is as effectively isolated from that of 

 another as is the colouring in a piece of agate. Likewise in the 

 barb and rachis pigment is definitely and permanently located 

 either in the solid cortex or in effectively separated cells of the 

 medulla, and there are no pores large enough to permit the passage 

 of melanin granules. The characteristic longitudinal arrange- 

 ment of melanin granules, which one finds at the close of 

 cornification of the feather, is permanent. . . . When the 

 feather is completed the dermal pulp possesses no functional 

 connection with it ; the barbs and barbules arc then isolated 

 from the vital processes of the organism, and have no further 

 power of groivth. 



" i . Most feather pigments are too resistant to chemical 

 re-agents to warrant belief in their solution and redistribution. 



" 15. Before cornification has ceased all the pigment which 

 the feather is ever to receive has been supplied to the cells 

 composing its fundament. 



" 16. Changes in the colour of plumage may take place — (1) by 

 a moult, during which the new feathers may have the same 

 pigmentation as their predecessors or a different one ; (2) by a 

 loss of certain portions of the feather ; or (3) by physical 

 disintegration in the cortex of the feather as the result of 

 exposure. There is no satisfactory evidence of a process of 

 re-pigmentation, and the histological conditions of the feather 

 render such a process highly improbable." 



All who read Dr. Strong's paper will be disposed to agree 

 with the verdict of the editor of The Auk, that it is " one of the 

 most noteworthy ornithological papers of the year." But even 

 though the passages I have italicized are so definite in expression 

 that they would hardly have been used by a scientific man who 

 was not absolutely certain as to his premises, one may be 

 pardoned for doubting whether the last word has been said 

 on the subject. The range of birds examined has been com- 

 paratively small, and the results of further research will be 

 anxiously awaited. — H. KENDALL. 



