212 Hans Gadow: 



My detailed explanation of the phyletic and morphological 

 meaning of the succession of feathers has hitherto been oral only. 

 Quite recently it has recieved an unexpectedly complete support, 

 amounting to proof, through the discovery by Frieda Bornstein^) 

 of the „Federleiste", the ectodermal germinal ridge or Strand 

 which forms the feathers, and through which the germs of all 

 the generations of any particular feather are continuous, from the 

 neossoptile to the first, and from tliis to the last member of an 

 apparertly inexhaustible series of teleoptiles! 



The ,, Federleiste" behaves much Hke the dental ridge of Mam- 

 mals, but in stead of producing germbuds which are packed side 

 by side and then lose connexion which each other, the feather- 

 germ ridge behaves rather hke the growth of a perennial bulbous 

 plant, for instance a Scilla, which, as is well known, thereby sinks 

 from year to year deeper into the gromid. Further, instead of 

 several, only one germ for a future feather is laid down at the 

 time. The papilla of the first teleoptile is already forming whilst 

 the neossoptile is still growing! 



This conti nuity between two successive generations of feathers 

 is absolute until tlae present feather has fim'shed its growth. The 

 pulp is reduced, or shrunk down to the base and there closes the 

 socalled lower navel of the quill. During the foUowing prolonged 

 period of rest there is probably no hve connexion, authough if 

 a perfectly adult, old feather be puUed out, its navel will always 

 be found to be soft and torn, whilst if this quill is moulted, it 

 leaves the pocket with a hardened and finished navel base. 



This long-protracted continuity may throw light upon a still 

 very obscure point. It makes it reasonable to assume that a 

 modification of the growing feather, induced by external, environ- 

 mental, conditions, may also similarly affect the next generation, 

 although to a lesser extent. Lesion of the pulp, within the blood- 

 quill, sometimes causes abnormal growth or coloration in the 

 successor. It is not excluded that some enthusiasts may take 

 such a case as one of an inherited acquired character. 



Frl. Bornstein's observations are not quite perfect in so far 

 as she does not mention the continuity of the barbs of the nestling 

 down with those of the following feather. The conditions repre- 

 sented in her Fig. 12 would indeed seem to make such a con- 

 tinuity impossible, but this difficulty is apparent only, not real. 

 We must remember that it is always the basal portion of the 

 papilla which produces the featherbuilding cells, whilst the apical 

 portion is inactive. This must be so, since the top of the pulpa 

 proper, covered only by the basal membrane, projects out through 

 the Upper navel. Thjs circumstance may further help to exp]ain 



^) Über Regeneration der Federn und Beziehungen zwischen Federn 

 und Schuppen. Archiv f. Naturgeschichte. 77. Bd. 1. 4 Supplement. 1911. 



