216 Hans Gado\A': 



and further that repeated Splitting of the primary branches of 

 rami has produced the radii and ultimately the cilia and hooklets. 



We had satisfied ourselves in the first part of this paper that 

 there is, or was, absolute continuity between the successive gene- 

 rations of feathers. The formation of a spool may therefore be 

 looked upon as originally the result of a periodic arrest of sphtting 

 proliferation. 



Further stages concern only the perf ecting of this still primitive 

 brush-like neossoptile into a typical feather; the arranging of at 

 first equivalent rami onto a shaft and the consolidation of the 

 spool with its ine: dental advantages. 



The first solid cornified cone, the first hollow cone and the 

 sheath of each succeeding feather are continuous, products of the 

 same outer layer (itseK composed of several layers, or thiclaiesses 

 of cells) of the proliferating papilla, and as such they are homo- 

 logous with the periodically cast off skin of the Snakes, or the con- 

 growing „Tortoiseshell" of Chelonians. But whilst in Reptiles the 

 basal membrane is soon abolished through the establishment of 

 an intermediate layer, due to immigration of ectodermal elements 

 into the corium, in the birds' feather-foUicle the basal membran 

 remains intact; and in correlation with the elaborate follicular 

 pocket with papilla, it has become possible for an inner, deeper 

 mass or layer of cells to produce a second cornified cone within 

 the first, and at the same time. As explained before, periodic 

 growth of this second, inner layer, produces the Neossoptile and 

 its continuation the Teleoptile. Lastly, with an innermost layer 

 we arrive at the basal membrane, which transforms itself into the 

 feather-soul, and this may well be looked upon as the represen- 

 tative of still another structure, a kind of future feather, at least 

 potentially if there were any need of troubling about super-feathers. 



When considered from an unbiassed point of view it is not 

 difficult to homologise the feather-sheath with the ,, inner root 

 sheath" (innere Wurzelscheide, composed of Henle's and Huxley's 

 layer) of the Mammalian hair, just as much as the hair is homo- 

 logous with the feather. There is however this d'fference that the 

 sheath of the hair now appears reduced in comparison with the 

 sheath of the feather and that its cells do not form a solid cornified 

 mantle. In some respects the hair is precocious, it pierces its sheath 

 at an early stage ; in others it appears simpler (more primitive ?) 

 than a feather, as it is never branched and remains at the solid 

 cone stage with only a very short pulp. Even this difference dis- 

 appears when the hair assumes the d'mens'.ons of a spine with 

 the starshaped constrictions, or expansions of its elongated pulp. 

 It may as well be mentioned that the ,, Oberhäutchen" of the 

 hair is not the same as the epitrichium. 



The notorious attempt to derive the MammaKan hairs from 

 some hind of pre-reptilian sensory apparatus, analogous to the 



