1917] 



The Ottawa Naturalist. 



153 



Bottom Environment. 



Analysis of the data given in the preceding table will show that 

 different types of sea bottom are occupied by assemblages of animals 

 which are almost as sharply contrasted in composition as are the land 

 faunas of deserts and swamps. On land some plants can live only on 

 wet marshy ground; other groups require dry uplands, and some 

 flourish only on rocky slopes; while over great areas which support a 

 rich flora trees cannot exist. The groupings of land animals is controlled 

 in the same way directly by the character of the soil and indirectly by 

 the plant life which itself is almost wholly influenced by surface 



