APPENDIX 



obtained from the embryos of Chinese geese in which the 

 legs are relatively longer than in penguins. In a 13-days 

 goose embryo the whole of the skin below and for some 

 distance above the tarsal joint is quite smooth, whereas the 

 skin of the rest of the leg is studded with feather papillae. 

 On the other hand, in an i8-days goose embryo in which 

 the' feather papillae of the legs have developed into fila- 

 ments, each containing a fairly well-formed feather, scale 

 papillae occur not only on the foot below and for some dis- 

 tance above the tarsal joint but also between the roots of 

 the feather filaments between the tarsal and the knee joints. 

 More important still, in a 20-days goose embryo a number 

 of the papillae situated between the feather filaments of the 

 leg were actually developing into scales each of which over- 

 lapped the root (calamus) of a feather just as scales overlap 

 the foot feathers in grouse and other feather-footed birds. 



" As in bird embryos there is no evidence that feather 

 papillae ever develop into scales or that scale papillae ever 

 develop into feathers it may be assumed that feather papillae 

 are fundamentally different from scale papillae, the differ- 

 ence presumably being due to the presence of special 

 factors in the germ-plasm. Just as in armadillos hairs are 

 found emerging from under the scales, in ancient birds as 

 in the feet of some modern birds the coat probably con- 

 sisted of both feathers and scales. But in course of time, 

 owing perhaps to the growth of the scales being arrested, 

 the coat of the birds, instead of consisting throughout of 

 well-developed scales and small inconspicuous feathers, 

 was almost entirely made up of a countless number of 

 downy feathers, well-developed scales only persisting be- 

 low the tarsal joint. 



" If the conclusions arrived at with the help of the 

 Emperor Penguin embryos about the origin of feathers 

 are justified, the worst journey in the world in the interest 

 of science was not made in vain." 



END OF VOLUME ONE 



Printed in Great Britain hy R. & R. Ci.ark, Limited, Etiinhurgh. 



