268 



PROTOZOANS. 



Fig. 514. — (;re- 



garina. Fig. 515. — Fig. 516. — Portion of 



Sphxrozoum. Fig, 515, magnified. 



Fig- 517- — Podocyrtis. 



Fig. 51S. — Lagena. 



Fig-sig — Amoeba. ' / /f " Fig. 521. — Niimmulite. 



Fig. 520. — Pol3-stomella. 



521, is one of the Rhizopods or Foraminifers, which 

 has a shell half an inch or more in diameter in some 

 cases, and divided into chambers which resemble those 

 of a Nautilus or Ammonite. E.xtensive beds of lime- 

 stone are made of Nummulites, that of which the 

 Pyramids of Egypt are built is filled with shells of this 

 sort. The Amoeba, Figure 519, is a Rhizopod which 

 has no shell. It is a simple, almost fluid mass, seen 

 only by the aid of a microscope, and it changes its 

 form almost every moment. It has neither mouth 



