666 DR. H. GADOW ON THE REMIGES OF BIRDS. [DeC. 18, 



feathers have been turned ventralwards around the posterior or uhiar 

 margin of the wing, and that these birds have retained a primitive 

 condition. If we mark the last dorsal posterior series of the Pen- 

 guin's potential primaries with A, then A will in Siruthio represent 

 the only existing series of greater under coverts, whilst the primaries 

 of Struthio have to be marked B. This series B has overgrown the 

 series A, as is already indicated by the fact that in the Penguins the 

 last but one series, viz. B, contains somewhat larger feathers. Lastly, 

 in the majority of Carinatse A and B represent the larger under 

 coverts, and the series C, i. e. the third last of the Penguins, has been 

 developed into the series of primaries, whilst series D forms the upper 

 larger wing-coverts. 



This would mean of course that the Penguins retain a condition 

 which in other birds is referred to their embryonic life, whilst Struthio 

 represents an intermediate stage, provided, however, that in Struthio 

 no secondary reduction from several to one series of under wing-coverts 

 has taken place. Such a reduction I assume in Rhea, and likewise in 

 the Oscines, which possess only one row of larger under wing-coverts. 

 However, Mr. Wray has shown that Struthio shows various conditions 

 which in the Carinatge are repeated during their embryonic growth 

 only. 



Unfortunately, about the embryonic development of the Penguin's 

 wing we know nothing ; we cannot explain either the enormous 

 number of series of the wing-featiiers nor the number of the feathers 

 in each series ; we have to look upon them as the result of special 

 modifications. There is no reason why the skin of the wing should 

 not develop any number of feathers. Concerning the cubital quills, 

 we know that their number increases with the length of the fore- 

 arm, the additional increase in number taking place in the region of 

 the elbow. 



Archceopteryx does not throw much light upon the question. It 

 possessed 6-7 primaries, most of which were carried by the third me- 

 tacarpal and by the third finger. The number of cubitals was 10. 



The first Reptile-like Birds probably possessed a rather uniform 

 covering of feathers on their wings. The feathers of the under 

 surface were soft, more downy, those of the upper surface stronger and 

 smoother. The first feathers which grew out stronger and larger 

 were those on the upper hinder margin of the forearm ; this resulted 

 in a protection of the sides of the body, and in the possibility of 

 these feathers being occasionally used as a parachute. Natural selec- 

 tion preserved and improved these advantageous acquisitions, in a 

 similar way as the scales on the hinder margin of the "fins" of 

 Turtles are elongated and flattened out. Later on the elongation 

 and strengthening of the posterior marginal feathers extended over 

 the metacarpus and over the fingers, which at this stage were still 

 free and not anchylosed with each other. If these ancestral birds 

 possessed a cutaneous patagium, this was gradually restricted to the 

 proximal region between arm and trunk, where no remiges are 

 developed. Such a structure might have interfered with the folding- 

 up of the wing. 



