62 THE HISTORY OF CREATION, 
immense variety of forms, sometimes creeping at the bottom 
of the sea, sometimes swimming on the surface. Only very 
few live in fresh water (Gromia, Actinosphzerium). Most of 
them possess solid calcareous or flinty shells of an extremely 
beautiful construction, which can be perfectly preserved in a 
fossil state. They have frequently accumulated in such 
huge numbers as to form mountain masses, although the 
single individuals are very small, and often scarcely visible, or 
completely invisible, to the naked eye. A very few attain 
the diameter of a few lines, or even as much as a couple 
of inches. The name which the class bears is given 
because thousands of exceedingly fine threads of protoplasm 
radiate from the entire surface of their naked slimy body ; 
these rays are quasi-feet, or pseudopodia, which branch off 
like roots (whence the term Rhizopoda, signifying root- 
footed), unite like nets, and are observed continually to 
change form, as in the case of the simpler plasmic feet of 
the Amceboidea, or Protoplasts. These ever-changing little 
pseudo-feet serve both for locomotion and for taking food. 
The class of the Rhizopoda is divided into three different 
legions, viz. the chamber-shells, or Acyttaria, the sun-animal- 
cules, or Heliozoa, and the basket-shells, or Radiolaria. The 
Chamber-shells (Acyttaria) constitute the first and lowest of 
these three legions ; for the whole of their soft body consists 
merely of simple mucous or slimy cell-matter, or proto- 
plasm, which has not differentiated into cells. However, 
in spite of this most primitive nature of body, most of the 
Acyttaria secrete a solid shell composed of calcareous earth, 
which presents a great variety of exquisite forms. In the 
more ancient and more simple Acyttaria this shell is a 
simple chamber, bell-shaped, tubular, or like the shell of 
