Anatomy of the Penguins 93 



as an almost rigid body. However, most of the muscles which are present in 

 the wing of a flying bird are represented in the wing of a Penguin by tendons, 

 showing beyond question that the present flightless condition has been produced 

 by degeneration from an ancestor which enjoyed the power of flight. 



While the bones of the leg are modified to a less extent than are those of the 

 wing, they nevertheless present a number of peculiarities not met with in other 

 birds. Thus the knee-cap (patella) is larger than in most birds, while the tarso- 

 metatarsus is shorter and broader than in any known bird except the Frigate- 

 bird, and retains its three elements in an incompletely fused condition (Fig. 17). 

 In all other birds the fusion of these bones is not only complete, but in many 

 cases is carried to such an extent that all evidence of individuality has disappeared 

 and it appears as a solid bone. This incomplete fusion of the metatarsal bones 

 was present in the earliest known fossil representative (Palaeudyptes antarclicus 

 from the Eocene of New Zealand), which was thought to prove that modern 

 Penguins have directly inherited this feature, though with fuller knowledge this 

 seems to require modification. The toes, four in number, are all directed forward, 

 a condition not unknown among other birds, yet of rather uncommon occurrence. 

 When on land Penguins stand very erect, w T ith drooping wings, and the whole of 

 the metatarsus is applied to the ground, thus making them very "flat-footed." 



Among other structural features it may be mentioned that the beak is usually 

 long and straight, with its sides compressed and more or less grooved, and its tip 

 never hooked but rather sharply pointed. The nostrils are slit-like and located 

 within lateral grooves, while the palate is also of the split (schizognathous) type. 

 The breast-bone, which is about half as broad as it is long, has a pair of notches 

 at the back and a well-developed keel in front. Of the four toes the first is very 

 small and joined to the inner sides of the metatarsus, while the other three are 

 strong and completely webbed. 



The feather-covering in the Penguins also affords another interesting feature. 

 With the possible exception of the Screamers they are the only known birds in 

 which there are no bare spaces (apteria). The feathers themselves are narrow, 

 lanceolate, with a very broad, flat shaft, convex beneath, with the ordinary fur- 

 row of the lower surface usually wanting. The aftershaft is distinctly recogniz- 

 able and is similar to the shaft. No specially formed quills can be detected in 

 the wings, but in the tail stiff quills are usually distinguishable. Beneath the 

 feathers or just under the skin are powerful muscles by means of which the water 

 can be entirely shaken from the feathers as the birds emerge from the icy sea, - 

 a fortunate provision, for otherwise, in the frigid temperature in which they live, 

 they would be masses of ice in a few moments. The body temperature, stated by 

 Mr. W. Eagle Clarke to be io2-io3 F., for the Adelie Penguin, is further 

 equalized and maintained by a dense layer of fat beneath the skin not unlike the 

 layer of blubber in seals and cetaceans. The moult takes place quickly, the 

 plumage peeling off, as it were, in large patches, and disclosing to view a short 

 undergrowth of new feathers, the whole process, according to Buller, requiring 

 only two or three days. Other observers place the length of time of actual shed- 

 ding as within ten days or two weeks. The moult of the King Penguin has been 



