ONE-CELLED ANIMALS 



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animals to appear on the earth, and as ocean life is older 

 than terrestrial life it is probable that certain marine Protozoa 

 are the most ancient of all animals. 



Some of these marine Protozoa, as the Foraminifera and the 

 Radiolaria, secrete a tiny shell of lime or silica which encloses 

 most of the body. When these animals die their shells sink 

 to the bottom where, as they slowly accumulate, they form a 

 thick layer over the floor of large areas of the ocean. The 



FIG. ii. A marine Protozoan, Rosalina variant (Foraminifera), with 

 calcareous shell. (Greatly magnified; after Schultze.) 



ooze thus formed is called Foraminifera ooze or Radiolaria ooze, 

 according to which order of Protozoa chiefly formed it. All 

 over the world are found great strata of rocks that are formed 

 almost exclusively of the fossil shells of these Protozoa. The 

 extensive chalk beds and cliffs of England, France, Greece, 

 Spain and America were made by Foraminifera, whose shells 

 were deposited there when these places were parts of the ocean 

 beds. The siliceous rock called Tripoli, found in Sicily, and the 

 Barbadoes earth from the island of Barbadoes are composed of 

 the shells of ancient Radiolaria. 



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