Fbbruary 23, 1900.] 



SCIENCE, 



297 



a granular blackish substance. The yel- 

 lowish stain was confined to the transparent 

 sheath of the barbs and to the barbules, 

 while the granular matter varied in place- 

 ment with the color of the feathers. 



An unchanged, i. e., fall-colored feather, 

 examined in a fresh state, exhibited the fol- 

 lowing appearance under the microscope. 

 Therhachis appeared, centrallj', to be cellu- 

 lar in construction with an enveloping 

 sheath thickly supplied with the black pig- 

 ment matter, the granules arranged in an 

 order suggestive of a streaming movement 

 toward the tip of the feather. At the junc- 

 tion with each barb a small portion of the 

 main system curved upward into the central 

 portion of that member. Proximally this 

 column ended in the modification of the 

 rachis into barbs. The center of each barb 

 of the colored parts of the feathers con- 

 tained a prismatic column, resembling to 

 my eye, a number of -bodies set together so 

 as to resemble the nodes and internodes of 

 a bamboo cane. At the distal end of each 

 barb these bodies tapered, and in many 

 cases the extreme joints were separated 

 fi'om the main column. About the blue 

 portions of the feathers, these columns were 

 massed thickly with black matter, the por- 

 tions giving the rusty effects being much 

 less plentifully supplied, and surrounding 

 this central column a transparent envelope 

 of the yellowish stain was present. The 

 barbules of the non-blue area were the color 

 of this sheath but became well supplied 

 with the dark pigment when the blue-pro- 

 ducing area was met with, completely ob- 

 scuring the presence of the stain. The tips 

 of the prismatic columns showed a pale 

 brownish orange color, but gradually as the 

 microscope slide was passed across the stage 

 the color became deeper until when one- 

 half of the length of the barbs had passed 

 before the objective, it appeared deep black. 



The blue area of such a feather gave a 

 good reaction for Zoomelanin (black), for 



by boiling the feather in KOH, 0.5% and 

 then heating with chlorine, the dark matter 

 was completely broken up, and the feather 

 appeared colored as with the rusty-colored 

 tip which was apparently unaltered by the 

 test. 



When compared to a feather wholly 

 changed to blue by the Aptosochromatic 

 process, a valuable suggestion is at once 

 thrown out, as to the nature of the change 

 of color. In a microscopic examination of 

 such a feather it is noticed that the lower 

 parts of the central barb colums were as in 

 the bicolored-fall feathers excepting that 

 the massing of the black appeared to be 

 denser. The upper parts however which 

 were deep orange brown before, varying to 

 lighter tints as the tips of the barbs were 

 approached, now appear thicklj' massed 

 with the black also, and the yellowish 

 barbules are likewise colored. The stream- 

 ing movement of the color granules is now 

 especially prominent in an activelj' chang- 

 ing feather, and it readily appears that the 

 rhachis gives up a part of its matter to the 

 barbs, which in turn supply it to the bar- 

 bules. A positive change of pigment is man- 

 ifested macroscopically, for a fall feather 

 held to the light or crushed, remains yel- 

 lowish in its yellow-colored parts, while a 

 spring feather, appearing entirely blue, so 

 treated, shows darkly, due to the addition 

 of black pigment. 



Undoubtedly the blue effects are pro- 

 duced by the prismatic column in coopera- 

 tion with the dark involved pigment, the 

 sheath enveloping these parts playing its 

 part with the barbules in producing the fall- 

 colored feather. A cross section of the blue- 

 producing barb sustains this view. When 

 placed under the microscope with all light 

 obstructed, but that descending to the stage 

 from above, the sheath became invisible 

 but the central column showed up like 

 phosphorus as a pale glimmering blue which 

 became opalescent with the varying quan- 



