26 Stuart-Sutherland, Pengitins. [,sf"iui — 



for in flying birds the principal stroke of the wings is downwards, 

 whereas in the Penguins it is upwards, so as to keep the bird under 

 water, for when 6n the surface the Penguin is only an indifferent 

 swimmer. This change of wing strokes has, of course, caused a 

 corresponding increase in the muscles which give the up-stroke 

 to the wing, and also an increase in the size of the shoulder-blade 

 (scapula). The wings are reduced to flippers, having no power 

 of flexure, the bones being broadened and flattened, and the first 

 and second digits are completely co-ossified. 



Worthy of special notice in this connection is the peculiar form 

 of the metatarsus, in which the three essential lengthwise bones 

 are incompletely fused together, being united only at their 

 extremities — a modification usually attributed to arrest of 

 development, for Prof. Gegenbaur's researches have shown that 

 the embryos of all birds possess these bones in an independent 

 condition. Prof. Newton inclines to the opinion that this is a 

 case of relapse produced in adaptation to the peculiar plantigrade 

 functions of the feet of these birds. 



As before mentioned, the legs are set far back, the tibia is hardly 

 visible, and the short thick toes are directed forward and con- 

 nected with a strong web, the small hallux being also turned 

 forward and joined to the tarsus by a very small web. 



The skull agrees with that of the Divers and Grebes in having 

 the palate of the schizognathous or cleft type ; the internasal 

 septum is incomplete, and there are hollows, on the forehead for 

 the reception of glands. The horny sheath of the maxilla is com- 

 posed of from three to five more or less distinct pieces according 

 to the genera, while the powerful bill may be long, thin, and 

 slightly decurved, as in the members of the genera Aptenodytes. 

 and Pygoscelis., shorter and fairly stout in Catarrhades, and very 

 stout, short, and compressed, as in Sphenisciis, where the prominent 

 hook of the culmen overhangs a truncated mandible. 



The furcula or " wish-bone" is U-shaped. The organ of voice 

 consists of one pair of tracheo-bronchial muscles, arising from the 

 windpipe and attached to the bronchial semi-rings. The tongue, 

 which is rudimentary, is very much reduced in some members 

 of the family. 



On the body we find no naked tracts, but a uniform covering of 

 small scale-like feathers with or without barbs', and an equally 

 uniform distribution of down both in the adults and young. 

 Even more striking are the wings, which are totally devoid of 

 normally developed quills, though the number of leathers is very 

 large, the primaries amounting to 36, being more numerous than 

 the quills or wing coverts of any other known bird. The process 

 of moulting is very peculiar, and is accomplished in an exceptional 

 manner, the plumage being shed in patches, and that of the wings 

 gradually flaking off above the new coat. The time occupied in 

 the moulting process varies in the different species, but is seldom 

 longer than fourteen days ; seven to ten days is the usual. As the 

 bird never enters the water during the moulting period, and 



