W. p. PYCRAFT: POWDER-DOWN OF HERON. 345 



feathers are known as "powder-down " feathers, and are 

 found in patches distributed in three j)airs over the body. 

 The first, and largest, pair is hidden by the breast 

 feathers. When these are pushed aside, the patches will 

 be found lying on either side of the middle line and 

 extending backwards as far as the middle of the sternum, 

 and forwards on to the interclavicular air-sacs at the base 

 of the under-side of the neck. The second pair is seated 

 on the thigh, the area covered being triangular in shape 

 and corresponding to the fleshy portion of the thigh, from 

 the line of the femur backwards. The third pair is quite 

 small, linear in shape, and inguinal in position. 



When the skin of the body is removed, the roots of 

 these remarkable feathers are seen to form closely packed 

 masses, dark in colour, and rich in oil. 



The friable nature of the feathers has already been 

 alluded to, and it is generally believed that it is by this 

 ready disintegration of these feathers that the powder is 

 formed. That the tips of the feathers, in short, break up 

 into an exceedingly fine powder. Under the microscope 

 this powder has an exceedingly fine granular appearance, 

 and as far as I have tested it, is insoluble in ether or 

 benzole. To the touch it is generally described as 

 greasy, but waxy would be a more accurate simile. 



From the feather itself, even under a high power of the 

 microscope, I have so far been able to gain but little 

 information. The rami are exceedingly long and almost 

 devoid of radii. Towards the tips the rami commonly 

 take on a curiously zig-zag form, the preliminary stage, 

 apparently, to disintegration. 



As to the purpose and origin of these feathers, nothing 

 is yet known ; though I hope, in a later communication in 

 the near future, to be able, if not to solve, at least to 

 point the way to a solution of the problem. I suspect 

 that the powder will be found to be derived from the 

 disintegration of the outer layer of the rami, or feather 

 barbs, for it bears a close resemblance, in many respects, 

 to the friable sheath which invests growing feathers. 



