BRANCH PROTOZOA: THE ONE-CELLED ANIMALS 81 



other, thus forming a sort of protoplasmic network outside 

 of the shell. In some cases there is a complete layer of 

 protoplasm part of the body protoplasm of the Protozoan 

 surrounding the cell externally. 



When these tiny animals die their hard shells sink to 

 the bottom of the ocean, and accumulate slowly, in in- 

 conceivable numbers, until they form a thick bed on the 

 ocean floor. Large areas of the bottom of the Atlantic 



FIG. II. Rosalina varians, a marine protozoan (Foraminifera) with calca- 

 reous shell. (After Schultze.) 



Ocean are covered with this slimy ooze, called Forami- 

 nifera ooze or Radiolaria ooze, depending on the kinds of 

 animals which have formed it. Nor is it only in present 

 times that there has been a forming of such beds by the 

 marine Protozoa. All over the world there are thick 

 rock strata composed almost exclusively of the fossil shells 

 of these simplest animals. The chalk-beds and cliffs of 

 England, and of France, Greece, Spain, and America, 

 were made by Foraminifera. Where now is land were 

 once oceans the bottoms of which have been gradually 



