1883.] 213 [Jeffries. 



out by Schroeder, though I have not seen his paper. Here it is 

 well to note that the wing and tail feathers of birds which 

 remain in the nest grow from the first like those of adult birds, 

 e. g. Passares, Picariae, Accipitres and the like ; on the other hand 

 in birds which leave the nest they are preceeded by regular down 

 feathers like those on the rest of the body. Secondly, the rela- 

 tion of the various parts of the feather to the parts of the adult 

 skin, as pointing out the value of the divisions in the epiderm. 



Thirdly, as a feather on an adult bird is a successor or contin- 

 uation of a down-feather, the two may be regarded as repre- 

 senting the embryology and development of the feather. That 

 is, assuming the down-feather to be nearer the form of the 

 primitive feathers, the feathers of adult birds may be regarded 

 as their evolved descendants. And thus we are able to see 

 how far their embryology — i. e. growth of adult feathers — coin- 

 cides with their evolution. 



That the above assumption is correct I shall endeavor to show 

 in the latter part of this paper. 



So far as I know, the development of feathers never begins 

 after a bird has left the egg. All the feathers-sacks seem to be 

 formed during embryonic life. In this paper attention has been 

 chiefly turned to the growth of the remiges and rectrices, though 

 the common contour feathers have not been ignored. Much to 

 my regret I have not been able to study the formation of any of 

 the peculiar structures, as the waxes of certain forms of the 

 Ampelidae. 



The first step towards the formation of a new feather is the 

 growth of the old papilla, which, after the perfection of the 

 previous feather, shrinks to a small mass at the base of the feather. 

 The papilla, by simply elongating forces out the old feather and 

 with it the horn cells forming the inner coat of the feather 

 pocket. I use this word in distinction to the feather sack, or 

 coat, of a pin-feather. In every case examined by me the first 

 step has been that described above. I have never seen a papilla 

 developed below or beside the old feather as usually described 

 for hairs, and as described by some for feathers. Again, accor- 

 ding to my observations, the old feather is always forced out of 

 the pocket by the growing pulp. The little feathers wiiich 

 Studer describes as growing out of the pockets beside the old ones 



