Distribution of Sturgeons. 25 



special zoological province, including the antarctic Fauna, 

 which, in a great measure, corresponds to the arctic Fauna 

 in its uniformity, though it differs from it in having chiefly a 

 maritime character, while the arctic Fauna has an almost 

 entirely continental aspect. 



The fact that the principal races of man, in their natural 

 distribution, cover the same extent of ground as the great 

 zoological provinces, would go far to shew that the differ- 

 ences which we notice between them are also primitive ; but 

 for the present we shall abstain from further details upon 

 a subject involving so diflScult problems as th« question of 

 the unity or plurality of origin of the human family, satisfied 

 as we are to have shewn that animals, at least, did not ori- 

 ginate from a common centre, nor from single pairs, but 

 according to the laws which at present still regulate their 

 existence. 



Additional Illustrations of the Geographical Distribution of 



Animals. 



I. — Geographical Distribution of Sturgeons* 



The sturgeons are generally large fishes, which live at the bottom 

 of the water, feeding with their toothless mouths upon decomposed 

 organized substances. Their movements are rather sluggish, resem- 

 bhng somewhat those of the cod-fish. 



Their geographical distribution is quite peculiar, and constitutes 

 one of their prominent peculiarities. Located as they are, in the 

 colder portions of the temperate zone, they inhabit either the fresh 

 waters or the seas exclusively, or alternately both these elements, — 

 remaining during the larger part of the year in the sea, and ascend- 

 ing the rivers in the spawning season. Although adapted to the 

 cold regions of the temperate, they do not seem to extend into the 

 arctic zone, and I am not aware that they have been observed in 

 any of the waters of the warmer half of the temperate zone. The 

 great basin of salt-water lakes or seas which extends east of the 

 Mediterranean, seems to be their principal abode in the Old World, or 

 at least the region in which the greater number of species occur ; 

 and each tpecies takes a wide range, extending nn the Danube and 

 its tributaries, and all the Russian rivers emptviiig into the Black 



* Agassiz's Lake Superior, p. 2G4. 



