16 



FIRST LESSONS IN ZOOLOGY. 



mud or ooze, forming the bottom of the ocean at great 

 depths: this soft, deep mi}d is called Globigerina ooze. 

 Chalk is largely made up of the calcareous shells of Fora- 

 minifera; before it became hardened into rock-masses it was 

 a kind of Foramiuiferous ooze. 



Certain root-animalcules secrete a silicious shell; a few 

 live in fresh-water ponds, but the majority live in the sea. 



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FIG. lO.Potalia. A Rhizopod, showing the pseudopodia. 



Their shells possess wondrous beauty and variety of orna- 

 mentation. 



A few root-animalcules have been seen to develop from 

 little monad-like germs, which move about by means of 

 two little threads or tails. 



All the root-animalcules form the class of Protozoa known 

 as Rhizopoda, since all move by root-like pseudopods, and 

 nearly all, except Amceba, are protected by shells. 



