Page:The Worst Journey in the World volume 1.djvu/436

Rh into the first generation of feathers correspond to the papillae which in lizards develop into scales?

"The late Professor Assheton, who undertook the examination of some of the material brought home by the Terra Nova, made a special study of the feather papillae of the Emperor Penguin embryos from Cape Crozier. Drawings were made to indicate the number, size and time of appearance of the feather papillae, but unfortunately in the notes left by the distinguished embryologist there is no indication whether the feather papillae were regarded as modified scale papillae or new creations resulting from the appearance of special feather-forming factors in the germ-plasm.

"When eventually the three Emperor Penguin embryos reached me that their feather rudiments might be compared with the feather rudiments of other birds, I noticed that in Emperor embryos the feather papillae appeared before the scale papillae. Evidence of this was especially afforded by the largest embryo, which had reached about the same stage in its development as a 16-days goose embryo.

"In the largest Emperor embryo feather papillae occur all over the hind-quarters and on the legs to within a short distance of the tarsal joint. Beyond the tarsal joint even in the largest embryo no attempt had been made to produce the papillae which in older penguin embryos represent, and ultimately develop into, the scaly covering of the foot. The absence of papillae on the foot implied either that the scale papillae were fundamentally different from feather papillae or that for some reason or other the development of the papillae destined to give rise to the foot scales had been retarded. There is no evidence as far as I can ascertain that in modern lizards the scale papillae above the tarsal joint appear before the scale papillae beyond this joint.

"The absence of papillae below the tarsal joint in Emperor embryos, together with the fact that in many birds each large feather papilla is accompanied by two or more very small feather papillae, led me to study the papillae of the limbs of other birds. The most striking results were