370 BRITISH BIRDS. [vol. vi. 



at different times ; (3) individuals vaiy both in the extent 

 to which old feathers are cast and new ones acquired, as well 

 as in the intensity of colouring and markings ; (4) the feathers 

 themselves in the same region of the body vary greatly, and 

 it is therefore impossible to prove " colour-change " by com- 

 paring individual feathers. 



Mr. Millais states in the work under review, that Mr. 

 Pycraft has microscopically examined feathers and is unable 

 to find " any channels by which colour or ' life ' can be passed 

 up the quill and the rami,^^ but, adds Mr. Millais, he has 

 admitted that his microscope is not a very powerful one. 

 Mr. Millais is evidently unaware of the very careful and 

 prolonged investigation on " The Development of Color in 

 the Definitive Feather " undertaken by Mr. R. M. Strong at 

 the Museum of Comparative Zoology at Harvard College, 

 U.S.A., under the direction of Professor E. L. Mark.* 



In our judgment this investigation disposes of the possi- 

 bility of re -pigmentation or redistribution of pigment in 

 a feather. Mr. Strong's paper is long and highly technical 

 but we may with advantage quote the following conclusions 

 from the section devoted to " Change of color Avithout 

 Molt," more especially as many British ornithologists appear 

 to be ignorant of Mr. Strong's investigations :— 



" The arguments against change of color without molt through repig- 

 mentation or regeneration of pigment may be summed up as follows : — 



1. Most feather pigments are too resistant to chemical reagents to 



warrant belief in their solution and redistribution. 



2. Pigmentation of the feather has been observed to take place only 



in the younger stages of the feather germ. 



3. At the end of comification melanin granules have a definite 



arrangement, which is permanent. 



4. When comification has ensued, the varioas elements of the feather 



are hard, more or less solid, structures, and their pigment 

 contents are effectually isolated from one another. 



5. There is no satisfactory evidence of the occurrence of repigment 



ation, and all the histological conditions render such an event 

 highly improbable." 



We have been led away from the Diving Ducks along 

 what is after all only a side-issue by the author's firm belief in 

 colour-change without a moult. Mr. Millais's book remains 

 as a fine expression of ornithological art and observation. 



H. F. WiTHERBY. 



* " The Development of Color in the Definitive Feather." By R. M. 

 Strong. Bulletin of the Museum of Comparative Zoology at Harvard 

 College, Vol. XL., pp. 147-180, plates 1-9 (1902). 



