‘“¢ROLIPSE” PLUMAGE IN THE MALLARD. 37 
change, though the lustre has partly disappeared from the vertex, 
which is dark; and there is a little lightening of the lower 
chestnut feathers of the breast, which are tipped with white. 
There are three perfect curl feathers in the tail, and the old 
wing-feathers are quite firm and exhibit no tendency to be shed. 
August 18th, 1907.—Much of the gloss on the vertex, and 
some of that on the cheeks, is retained; the breast is partly in 
winter, partly in eclipse plumage; the abdomen is in full 
winter plumage. There are some dark feathers on each flank. 
September 11th, 1907.—The general aspect is that of a bird 
not quite in winter plumage; the head and neck are partially 
glossy, though there is still a good deal of brown upon the cheeks. 
There are some eclipse feathers in the breast, but the greater 
part are vermiculated and more winter feathers are coming 
through the down. The abdomen and the posterior part of the 
breast are completely vermiculated. There is one curl feather in 
the tail, and the tail-coverts are glossy. This bird was killed on 
September 12th, 1907. It presented a single graft the size of a 
small haricot: the tubuli were large and full of cells; in every 
tubule spermatogenesis was in active progress. 
(No. 7.) Bird in full winter plumage; castrated April 5th, 
1907. The testes were large and very soft, as when in full 
activity during this month. 
On April 21st it was noted that there was a brownish wash- 
like tinting of feathers on the lower breast and abdomen. 
July 27th, 1907.—Eclipse not complete. Some gloss on the 
vertex and cheeks ; the white ring has disappeared. The chestnut 
area of the breast is only partially in eclipse. A number of eclipse 
feathers are coming through, though many look vermiculated. 
A large number of vermiculated feathers persist in the flanks, 
and there are many new vermiculated feathers in this position. 
Vermiculated feathers are coming through at the bases of the 
wings. The hinder part of the breast is greyish rather than 
vermiculated ; no new feathers are coming through here. There 
are no curl feathers in the tail; the central feathers are ridging. 
The wing-feathers do not appear to have been as yet shed. 
November 30th, 1907.—Bird in full male plumage ; three curl 
feathers in the tail. The bird was killed and examined. There 
were a few encapsulated blood-clots about the site of operation, 
but no trace of the testes except two nodules situated close 
together and each the size of a millet seed. There were no 
nodules on the intestines or liver. Microscopic examination of 
the nodules referred to proved that they consisted of testicular 
tissue, some of the tubuli of which were distended with cells. 
No spermatozoa were present, and the central cells of the larger 
masses were degenerated. 
