58 NATURAL HISTORY OF BIRDS. 



may be readily expelled from the interstices of the plumage so soon as the bird quits 

 the water. Were it otherwise, in the low temperature of the Antarctic region, which 

 the majority of these birds inhabit, the plumage would soon be frozen into an icy 

 mass, the high temperature of the bird being of itself insufficient to obviate this, 

 although assisted by the great development of the subcutaneous fatty layer, which far 

 exceeds in thickness that of the corresponding structure in the member of any other 

 group of birds, and recalls to mind the fatty deposit or 'blubber' of the seals and 

 cetaceans. 



The cutaneous system is thoroughly characteristic of the group, find differs from 

 that of every other order of birds, in' respect of the uniform distribution of the 

 feathers over every part of the integument, and in the consequent absence of the bare 

 tracts or apteria met with in other birds. The feathers, which are narrow and rigid, 

 each possess an aftershaft. The remiges are not distinguishable from the surrounding 

 feathers, but the rectrices are clearly differentiated. 



ORDER V. - - PTILOPTERI. 



The superorder Impennes only comprises one order, the Ptilopteri, and the order 

 again only one family, the SPIIENISCID^E, the remnant of a group of birds, which, at an 

 earlier date of the earth's history probably played a more important role than nowa- 

 days, when they are represented by only a few genera with hardly more than twenty 

 species and subspecies. 



Being adapted in the highest degree to the life in the water, the penguins represent 

 among the birds the seals among the mammals, and curious indeed are the many fea- 

 tures in which the two groups show parallel developments both in structure and habits, 

 and particularly striking is the analogy with the eared seals, which chiefly inhabit the 

 southern hemisphere, like the penguins, the distribution of which is exclusively con- 

 fined to that part of the globe. It is a significant fact that the penguins are totally 

 absent from all seas washing the shores of continents or continent-like islands, where 

 no members of the Struthious superorder are now living, or have existed during the 

 present geological period. 



Like the fur-seal and its allies, the penguins pass the greater time of their lives on 

 the ocean, heedless of storm and waves ; down into the deep they go in pursuit of 

 their food, and down they go into the quiet regions never stirred up by any hurricane, 

 if the surface is getting too turbulent, though it must be hard weather indeed when a 

 penguin goes in search of shelter, for he enjoys the wildest surf and loves the roaring 

 gale. The swimming of the penguins is quite peculiar, and differs widely from the same 

 movement as performed by all other swimming and diving birds. It has already been 

 remarked that the paddle-shaped wings are brought in motion alternately, thus acting 

 like a screw, but while in other birds the legs also come into play at least as accessary 

 propulsive organs when the bird is diving, these organs in the penguins only act as a 

 rudder, except when swimming on the surface of the water. 



Neither are the legs very well adapted for rapid locomotion upon land, for the 

 leg proper is almost wholly included within the skin of the body, and the foot is broad 

 and clumsy, and the metatarso-phalangeal articulations so stiff that the whole tarsus 

 is applied to the ground when the bird is walking, a condition unknown among other 

 birds. The penguins are plantigrade, and their peculiar upright position when on 

 land is due to that unique arrangement. It is mainly for the purpose of propagation 

 that their legions go ashore a short season every year, enlivening the desolate rocks 



