464 



THE ZOOLOGIST. 



of cellular ceratin or feather substance slightly pigmented with 

 melanin. From this pigmented part arise the scanty barbules, 

 which are also charged with melanin, although never appearing 

 blue. Springing from the lower inner surface is a single stratum 

 of polyhedral cells. Fatio, who was the first to describe this 



x 500 



important element of blue feathers, employed the word email, 

 and used the happy term les plumes emailles for all blue or green 

 feathers ; all who have examined the feathers of the Kingfisher 

 under the microscope must have remarked their resemblance to 

 fine enamel. Around and above these polyhedral cells there is 

 a strong tubular and transparent sheath, which is, as the 

 diagram shows, simply a prolongation of the sides of the pig- 

 mented lower part of the barb. 



These cells are alone the source of the blue of the Kingfisher. 

 With care, the pigmented portion of the barb may be cut en- 

 tirely away, without any appreciable difference to the brilliancy 

 of the feather. This clearly proves that pigment is not always 

 an essential item of blue feathers. In the Kingfisher, as in 

 every other bird that I have examined, the transparent outer 

 sheath may also be removed without affecting the blue colour 

 beneath ; in the above bird the sheath is colourless, but in the 

 green feathers of some Parrots it is clear yellow. Here, again, 

 my experience has never agreed with Dr. Gadow's statement 



