656 TEGUMEXTARY ORGANS. 



albino peculiarities are naturalized, as in the wild swan, the 

 snowy owl, the alpine hare, the arctic fox, the polar bear. 

 Dull and sombre hues best suit nocturnal animals, as moths 

 and owls, rats and mice, bats and lemurs ; and the darkest 

 colours conceal the inhabitants of burrows and subterranean 

 caves, as beetles, toads, and moles, and the huge inhabitants 

 of the dark abyss, as walruses, seals, and cetacea. The most 

 lively and varied colours, and the brightest metallic lustres, 

 are developed in the diurnal species of tropical climes, as in 

 parrots and cockatoos, humming birds, and birds of paradise ; 

 and the hues appear often to be regulated by those of the 

 accompanying vegetation. The metallic lustre, so rare in 

 mammalia, is splendid in the chrysochloris. The reddish- 

 brown fleece of lions and pumas, caracals and tigers, and 

 most feline inhabitants of the deserts, resembles the decayed 

 leaves, or the light of the setting sun, or the sandy plains on 

 which they lie in watch for their prey. So that the proper- 

 ties of these extravascular parts, have extensive relations 

 to the internal economy of animals, and to surrounding 

 nature. 



The colours of the tegumentary parts of animals, depend- 

 ing upon living parasites in the body of the epidermic cells, 

 are most distinct in the plump condition of these in the rete 

 mucosum, and are alike obvious in the chick in ovo, on the 

 foetus in utero, in the developing feather yet concealed in its 

 thick sheath and deep cutaneous follicle, and in the hairs of 

 subcutaneous cysts, to which the chemical influence of light 

 has never penetrated. Indeed the entire structure, proper- 

 ties, and forms of the tegumentary parts of organized beings, 

 are regulated by laws as simple and uniform as those of the 

 most essential organs of vegetative life, and they are most 

 intimately connected with the living habits and the entire 

 history of the species. 



