58 NATURAL HISTORY OF BIRDS. 



iiiMj- 1h' i-fiulily cxjx'IKmI fnnii \]w interstices of the ]iluin:igc' so soon as the bird ijiiits 

 the water. Wi-ie it otherwise, in the low temperature of the Antarctic region, wliich 

 the majority of tliese hirds inliahit, the ]>lumagc wouM soon he frozen into an icy 

 mass, the liigli ten)j)erature of tlie l»iril heing of itself insurticienl to ohx iate this, 

 although assisted by the great {levelopment of the subcutaneous fatly 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 dejjosit or ' blubber' of the seals and 

 cetaceans. 



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

 IliMt of every other order of binls, in resj)ect of the uniform distribution of the 

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

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

 each j)ossess an aftershaft. The remiges are not distinguishable from the surrounding 

 feathers, but the rectrices are clearly differentiated. 



Order V. — PTILOPTERI. 



The sujierorder Impennes only eomi>riscs one order, the Ptilopteri, and the order 

 again only one family, the Spiiexiscid.e, the remnant of a gi'oup of birds, which, at an 

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

 days, when tlicy are rejjresented Ijy only a few genera with hardly more than twenty 

 sjiecies and subspecies. 



Being adai)ted 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 wliich the two grou|)s show ))arallcl 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, tlie distribution of which is exclusively con- 

 fined to that ])art of the globe. It is a significant fact that the jienguins are totally 

 absent from all seas washing the siiores of continents or continent-like islands, wliere 

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

 present geological jieriod. 



T.ike the fur-seal ;md its allies, the penguins pass the greater time of their lives on 



(111 can, heedless of storm and waves; down into the dce|) they go in jnirsuit of 



their fund, :incl down tlicy go into the ijuiet regions never stiiird up by any hurricane, 

 if the surface is getting too turbulent, though it must be hai'd weather indeeil when a 

 jjenguiu goes in search of shelter, for he enjoys the wildest sinf and loves the roaring 

 gale. Tlie swimming of the penguins is (piite peculiar, and differs widely from the same 

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

 remarked that the jiaildle-shajjed 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 

 l)ro]iulsive organs when the bird is diving, these organs in the j)engr.ins only act as a 

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



Neither are the legs very well ailaj)tcd for ra])id locomotion upon land, for the 

 leg pro])er is almost wholly included within the skin of the body, and the foot is broad 

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

 is ap](lied to the ground when the bird is walking, a condition unknown among other 

 birds. The penguins are i>lantigraile, and their ])eculiar upright i>osition when on 

 land is due to that unique arrangement. It is mainly for the ])urpo.se of j)ro]iagation 

 that their legions go asliorc a short season every year, eidivening the desolate rocks 



