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OF THE KAGU, SUN-BITTERN, AND BOATBILL. 473 
I shall attempt to show, there appears in all a certain forecast and inclination towards 
defined lines of tract as in the contour-feathers. 
The powder-down patches, which Mr. Bartlett, in his paper already referred to, 
mentions as being very profuse in the Kagu, I made a point of examining with 
diligence. Their presence I found even more numerous than he has recorded. In fact, 
except the distal ends of the wings and legs, it might be said, broadly speaking, that 
the entire cutaneous surface has received a sprinkling. 
In Eurypyga they appear on the whole to follow the distribution which obtains in Rhino- 
chetus. In this respect my observations differ from those both of Nitzsch and Bartlett. 
In Cancroma there are four pairs of patches, as stated by Bartlett; whereas Nitzsch 
describes and figures only three pairs. 
The manner of research which I have adopted in examining these powder-down 
patches has been much after the fashion which Nitzsch recommends as applicable to 
the investigation of the “ feather-tracts” and “ featherless interspaces.” 
First. The bird was minutely examined with its plumage entire. In this way the 
large patches were readily apparent, while the scattered shorter plumes were more or 
less detected in place among the “ contour-” and “ down-feathers.” 
Second. The skin was carefully plucked on the one side, the large contour-feathers 
previously being removed, excepting the remiges and rectrices, which were cut short 
by a pair of scissors. Then, after noting the appearance in this condition, the down- 
feathers, or “ semi- and filo-plumes,” were regularly pulled out one by one with a pair 
of forceps. The number, form, and direction of the powder-down patches were then 
sufficiently clearly displayed for drawings to be made. 
Lastly. The plucked half skin was removed; and upon its inside the roots of the 
powder-down patches could be followed throughout their areas with ease. 
Thus a single bird suffices for a fair examination. The one half of the body remains 
intact, and permits of any doubtful point being reascertained and corrected as com- 
parison of the opposite half goes on. 
The author of the very valuable monograph on “ Pterylographie” devotes an entire 
chapter in discussing the nature, position, &c. of the powder-down feathers and their 
tracts. His observations go to prove their presence in limited patches in the orders 
Accipitres, Passerine, Galline, and Gralle. Dr. P. L. Sclater has since shown that in 
the order Picariz two genera, Leptosoma and Podargus, have each powder-down feathers 
in a patch. 
Nitzsch, moreover, had already mentioned of some of the family Psittacide that they 
possess powder-downs ; but, as he expresses himself, these are “ scattered all over the 
body, and not collected into tracts,” as likewise occurs in Gypaétus barbatus among the 
Rapacious birds. 
Thus it would seem that the distinguished German ornithologist appreciated these 
peculiar feathers as being distributed in given tracts or patches. To quote his own 
VOL. VII.—PART VI. June, 1871. 3x 
