254 



THE SEALS. 



Arctic circle only for a short distance on the 

 cold coasts of North America. The eared 

 seals inhabit in the northern hemisphere only 

 the coasts of the Pacific, from Behring's 

 Strait to Japan on the one side, and to the 

 extremity of California on the other; in the 

 southern hemisphere again they are found on 

 all the Antarctic coasts, and are met with on 

 those of Chile and the states of the Argentine 

 Confederation in America, those of the Cape 

 in Africa, as well as on the shores of Australia 

 and New Zealand. All the shores of the 

 Arctic Ocean and the Atlantic, including the 

 Mediterranean and the Black Sea as well as 

 the inland basins above mentioned, are in- 

 habited only by seals proper, which also 

 extend over nearly the whole of the domain 

 occupied by the eared seals. Only the coasts 

 of Africa and the East Indies are wholly 

 destitute of seals. The seals proper are thus 

 the generally distributed type, while the 

 walruses and eared seals have more limited 

 ranges. 



Palseontology sheds but little light on the 

 origin of the seals. Their fossil remains are 

 extremely rare. In the upper Miocene of 

 France remains have been found, with respect 

 to which it is doubtful whether they should 

 be ascribed to eared seals or seals proper. 

 The other Tertiary remains belong indubi- 

 tably to true seals, and some fragments be- 

 longing to walruses have been discovered in 

 the glacial deposits of France and Virginia, 

 accordingly in districts pretty far south. 



The affinities connecting the Pinnipedia on 

 the one hand through the structure of the 

 limbs with the sea-otters, on the other through 

 the structure of the skull and teeth with the 

 bears, are most conspicuous in the eared seals. 

 The whole organization, as well as the late 



appearance of the type in the history of the 

 earth, lead to the presumption that the Pin- 

 nipedia represent a branch of the Carnivora 

 which has gradually diverged from the main 

 trunk through undergoing a process of special 

 adaptation to an aquatic life, and which still 

 retains a considerable number of characters 

 belonging to the carnivorous type. The 

 walrus certainly leads to the Sirenia through 

 the remarkable modification of its dentition; 

 but we see in this approximation rather a 

 result of the convergence of characters in 

 types originally distinct brought about by 

 adaptation, than a fact pointing to affinity of 

 stock. 



Since organic life in general has raised 

 itself from the depths of the water to the free 

 air, the fact of the adaptation of land animals 

 to an aquatic life would form a remarkable 

 anomaly if we had not a thousand examples 

 to show of retrograde development due to 

 special adaptations. Here this process of 

 degradation is manifested especially in the 

 structure of the teeth and limbs, which remain 

 in a less advanced state of development. 

 The continuance of the pulmonary respiration 

 is, without doubt, a proof of this declension 

 which has affected animals originally ter- 

 restrial. It is not at all likely that animals 

 originally aquatic should, while continuing to 

 live in the water, have exchanged the power 

 of breathing by gills for that of breathing by 

 lungs, whereby they are placed at a consider- 

 able disadvantage compared with the other 

 inhabitants of the water by the nece.ssity of 

 rising from time to time to the surface. But 

 it would be useless to spin any more specula- 

 tions of this kind, since, in consequence of 

 the absence of palaeontological facts, they kck 

 in a measure a solid foundation. 



