On the Origin of Feathers. 213 



ihe real meaning of Jones' point 5 of his summary. The necessary 

 continuity of the nesthng barbs with those of the first teleoptile 

 have to be looked for in that dark Strand of cells which border 

 the right side of the central white gap in Bornstein's Fig. 12. 



Until her discovery it was thought that portion of the whole 

 circumference of the papilla was reserved for, and remained 

 dormant until, the growth of the next feather. 



The behaviour of the ,, Federleiste" and the growing into it 

 of a new pulpa, enables us further to corroct the perverse notion 

 hitherto entertained about the homologies of feathers with 

 reptihan scales. 



,, Regelmäßig angeordnete Erhebungen der Lederhaut, von 

 der Epidermis überkleidet, bilden die erste embryonale Anlage, 

 welche von den bei Reptilien bestehenden Einrichtungen nicht 

 wesentlich sich unterscheidet. Diese Papillen gewinnen aber eine 

 bedeutende Länge . . . Von den Schuppen sind sie durch be- 

 deutendere Länge verschieden." (Gegenbaur. Vergl. Anat. d. 

 Wirbeltiere, I, p. 134.) 



The usual statem nt that feathers are modified reptilian scales 

 requi es several restrictions. The difference between reptilian 

 scales and feathers is that the bulk of the reptilian organ is com- 

 posed of connective tissvie, mesoderm, with a thin horny coat, 

 the share of the epiderm. The feather is an entirely ectodermal 

 product and its pulp is an extremly vascular apparatus which 

 is with drawn and vanishes without contributing any cell-material 

 to the feather. The feather is therefore homologous only with the 

 ectodermal portion of a scale or ,, Schuppe". 



It has been customary to homologise the pulpa of the feather 

 with the whole of the ,,Schuppenkoerper" or mesodermal portion 

 of the scale. Bornstein, by further elaborating Ghigi's view, has 

 shown that the feather represents only a small portion of the 

 epidermal scale. Sagaciously she has examined those structures 

 which alcne can be expected still to represent more or less inter- 

 mediate ancestral conditions, to wit the feather-producing scutes 

 of the feet. 



The history of the origin of feathers may now be told as 

 follows. 



The Initiation is taken by proliferation of a much restricted 

 portion of the epiderm at the apex, or at the imbricating edge 

 of a Scale. It is immaterial whether the resulting cornified 

 thickening is single or multiple. It need not at once have formed 

 a prominant cone, on the contrary it is advantageous to liken it 

 to a wart with its characteristic inward growing tendency. 

 Feathers, hairs, nails, scales, in short most growths due to ecto- 

 dermal prohferation show the tendency of sinking- in with their 

 base and this often leads to a more or less pocket like arrangement, 

 which with the additional necessity of a pulpa terminates in the 



7. Hefe 



