16 



FIBST LES80N8 IW 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- 

 minif era; before it became hardened into rock-masses it was 

 A kind of Foraminiferoiis ooze. 



Certain root-animalcules secrete a silicious shell; a few 

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



Pio. 10. — RotcUia. A Ehizopod, 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 ly root-like pseudopods, and 

 nearly all, except Amoeba, are protected by shells.* 



* Leidy: Fresh.- water Rhizopods of North America, 1879. — Haeckel: 

 Die Radiolarien, 3 vols., Berlin, 1863-88 ; Report on the Radiolaria of 

 H.M.S. Challenger, 1887. With the works of Schulze, Hertwig, 

 Carpenter, J. Muller, etc. 



