. The biology of birds. Birds. ^4 THE BIOLOGY OF BIRDS Professor Cossar Ewart's Recent Work.—Some of the observations made on the mallard and other birds by Professor Cossar Ewart show that we are far from security or clearness in regard to the succession of plumages, and we propose to sum up his more important conclusions. These have, of course, to meet the criticism of other investigators. The coat worn by newly hatched ducks and geese corresponds to the first or protoptile nestling coat of penguins. The second set (mesoptiles) is disappear- ing, though still represented on the wing. The win
. The biology of birds. Birds. ^4 THE BIOLOGY OF BIRDS Professor Cossar Ewart's Recent Work.—Some of the observations made on the mallard and other birds by Professor Cossar Ewart show that we are far from security or clearness in regard to the succession of plumages, and we propose to sum up his more important conclusions. These have, of course, to meet the criticism of other investigators. The coat worn by newly hatched ducks and geese corresponds to the first or protoptile nestling coat of penguins. The second set (mesoptiles) is disappear- ing, though still represented on the wing. The wing-quill protoptiles are complete feathers, with a calamus, a shaft, and an aftershaft. Though small, they are complete ; with short stiff, as well as long, slender barbs ; with well-developed and in some cases hook-like cilia; and with a well-developed aftershaft, the bar- bules of which bear cilia. Thus there is nothing degenerate about these protoptiles. But the mallard has mesoptiles (second set) well-developed as well 4.—A mesoptile (m) as protoptiles. They occur as wing- So^a p™,ip,ir(Nr <=°™rts and wing-quills. Both sets may be seen in the mallard duckling at the end of the sixth week, but all are usually lost before the middle of the eighth week. The nestling tail of the mallard duckling, of importance in early diving, consists at first of eighteen protoptiles. During the second week these are pushed from the skin by the tail-quills, or by vestigial mesoptiles. For the rest of their diving period (six weeks) the mallard ducklings use teleoptile tail-quills. There are vestiges of two tail-quill mesoptiles, so that even in the tail there is distinct evidence of two generations of Fig. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933.
Size: 1063px × 2351px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectbirds, bookyear1923
