30 



AMCEBA, VOETICELLA, PARAMECIUM 



One great group, or order, called Foraminifera, are nearly 

 all marine. The shells of these animals, in most species 

 composed of lime carbonate, have either one or two large 

 terminal openings or are perforated with many minute 

 openings. Through these minute holes there project long, 



deUcate protoplasmic threads, the 

 pseudopodia. These fine pseudo- 

 podia often unite to form a net- 

 work about the shell (Fig. 10). 

 The shells of many Foraminifera 

 are rather complicated in struc- 

 ture and present a variety of 

 shapes and patterns. Many of 

 them are divided into chambers. 

 Nevertheless, they are one-celled 

 Fig. 10.— One of the Forami- animals, because all the chambers 

 nifera with streams of proto- ^^^ connected with One another 



plasm (pseudopodia) project- 

 ing through openings in the SO that the protoplasm COnstl- 

 shell. After Schultze. ^^^^gg ^^^ ^^^^ ^^^^ ^j. ^^^^ 



The marine Protozoa are myriad in number of individuals. 

 One species especially, called Globigerina, lives in such 

 immense numbers in the sea, usually near the surface of the 

 water, that the dead shells, which are constantly falUng 

 downward, form a mud, or ooze, in some cases of consider- 

 able thickness, on the bottom of the ocean. The shells of 

 this animal are microscopic in size, and composed of hme 

 carbonate. In England and France, great beds of white 

 chalk exist to-day which, when examined under a mi- 

 croscope, prove to be composed almost whoUy of the shells 

 of globigerina and other minute Foraminifera. 



Slipper animalcule, or Paramecium. — UnUke the amoeba, 

 this protozoan has a definite shape. It is microscopic, but 



