FEATHERS OF PENGUINS. 



The degenerate features are found in the vane. Only a very narrow area on each 

 side of the shaft presents to the naked eye the characteristic appearance of a continuous 

 vane, this central portion being fringed on each side by a wide downy border, while the 

 tip of the feather is formed largely by long, flattened 

 rami devoid of radii, and produced by a splitting up of 

 the free end of the rhachis to form a series of rods, 

 arranged fan wise (fig. 2). By wear the length of these 

 rami is greatly reduced, and thus the shape of the feather 

 just before the moult differs somewhat considerably from 

 that which it originally bore. Partly by this wearing 

 away of the rami, and partly by the death of the 

 pigment contained therein, the colour change noticeable 

 between the feather of a moulting and a newly feathered 

 bird is due. 



The Microscopic Structure of the rami and radii. 



15 



i 



That the vane of the contour feathers of the pen- 

 guins represents a degenerate, degraded form of that 

 characteristic of carinate birds which possess full powers of 

 flight, is obvious. That is to say, the feathers of the 

 penguin can in no sense be held to represent a primitive 

 type of feather, but are unmistakably degenerate struc- 

 tures, bearing evidence to an earlier structural perfection 

 identical with that which obtains to-day among birds 

 that fly. In their degenerate characters they resemble 

 the feathers of the flightless Palseognathse (Ratitse). 



While among the feathers of birds that fly the rami 

 of the remiges and rectrices grow shorter as they reach 

 the tip of the shaft or main axis of the feather, so that 

 none project beyond it, in the penguins the rami of 

 what, possibly, answer to remiges show no such curtail- 

 ment, but, on the contrary, are of great length, and give 

 the shaft the appearance of breaking up distally into a 

 fan-shaped series of rami (fig. 2), thereby agreeing with 

 the contour feathers. 



The radii are less degenerate than in Struthio, for 



example, among the flightless birds ; inasmuch as those of the distal series still possess 

 their hooklets, though these are reduced both in number and size ; they arise, 

 however, as delicate, filamentous, curved processes from broad laminae, twisted so as to 

 lie with their flat surface upwards, as in functional remiges. The radii of the proximal 



o 2 



PIG. 2. THREE FIGURES OF ONE OP 

 THE SMALL FEATHERS FROM THE 

 PHE-AXIAL BORDER OF THE WING, 

 ENLARGED EESPECTIVELY 2, 15, 



AND 20 DIAMETERS. The most 

 highly-magnified figure includes 

 only the tip of the feather, and 

 shows the fan-like termination of 

 the rhachis. 



