APPENDIX 



into the first generation of feathers correspond to the 

 papillae which in lizards develop into scales ? 



" The late Professor Assheton, who undertook the ex- 

 amination 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. Draw- 

 ings 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 em- 

 bryos 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 ap- 

 peared before the scale papillae. Evidence of this was espe- 

 cially afforded by the largest embryo, which had reached 

 about the same stage in its development as a 1 6-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 ascer- 

 tain 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 Em- 

 peror 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 



