664 ZOOLOGY. 



It appears, then, that each continent has had from the 

 first its distinct assemblage of life, and thus opposing con- 

 tinents, such as South America and Africa, have fundament- 

 ally different faunae, because they have had a separate geo- 

 logical history. Though the climate, moisture, and extent 

 of forests of Brazil and the West Coast of Africa may, for 

 example, be nearly identical, the animals are of a different 

 type. At the present day, Australian trees may be trans- 

 planted to California, and nourish there, and camels from 

 the Orient may breed in Southern California, because at the 

 present day the climate and soil are so much alike in the two 

 countries. 



Distribution of Marine Animals. Nearly all that has 

 been said thus far applies to land animals. Marine species 

 are assorted into fauna? which are nearly as well marked as 

 terrestrial assemblages of species. The barriers restraining 

 them within their faunal limits are the temperature of the 

 water, this being modified more or less by the ocean-cur- 

 rents, the nature of the shore, whether rocky or muddy or 

 sandy, and the nature of the sea-bottom, whether also 



v * 



rocky, muddy, or sandy. Many marine animals live attached 

 to rocks and stationary pebbles, others are found only in 

 coarse or in fine sand, while the muddy bottoms of harbors, 

 bays, and gulfs, or the soft, deep ooze of the ocean-depths 

 harbor a different assemblage of mud-loving species. The 

 temperature of the water is the most important agency now 

 in operation in the limitation of marine animals. Thus 

 there is a tropical, north and south temperate, an arctic 

 and probably an antarctic zone, and these are, along the 

 shores of the different continents, subdivided into distinct 

 fauna?. For example, along the coast of Eastern North 

 America, the arctic or circumpolar fauna extends from the 

 polar regions to Labrador and Newfoundland ; a second, 

 the Acadian, to Cape Cod ; between Cape Cod and Cape 

 Hatteras another assemblage (the Virginian) is found ; from 

 Cape Hatteras to Southern Florida a fourth, and the Flor- 

 idan peninsula belongs to the tropical regions. Along these 

 different areas the water is of different temperatures. "We 

 also find a large proportion of circumpolar animals in the 



