GYMNOMYXA. 99 
Ameba is a type of the single class Ru1zopopa in which 
there are pseudopodia, and of the order Zodosa with blunt 
or lobose pseudopodia, but there are three other important 
orders to.which we may briefly allude. 
The Aedzozoa or sun-animalcules are usually spherical in shape; and 
are found in freshwater. The pseudopodia are long rays usually stiff- 
ened with an axial rod of silica. The central mass of protoplasm is 
vacuolated, and some have a hollow perforated shell like those of the 
next order, Nearly all are centro-symmetric. 
Fig. 33.—A HE LI0z0an (Actinophrys sol). 
The entire animal magnified. (Ad nat.) 
Vacuole. Nucleus. 
Pseudopodial 
Ray. 
Central Axis of. 
Pseudopodium. 
Note the central nucleus and stiffened pseudopodia. 
The second order is that of the Xadiolaria. They are marine pelagic 
organisms of microscopic size and have a siliceous skeleton of isolated 
pieces called sfzcules, or a continuous perforated shell through the holes 
of which the fine radiating pseudopodia protrude. The main mass of 
protoplasm has .a thin capsule dividing it into central and peripheral 
portions, and in the peripheral parts there are often found a number of 
minute algoid bodies called yellow-cells. They live and multiply in close 
organic unity with the radiolarian. Such a union is termed syzdzosds 
(see Chapter IX.). Radiolarians are commonly centro-symmetric, but 
some are axo-symmetric. Countless numbers of them live and die in 
the pelagic water, and their shells and spicules cover the sea-floor at 
great depths, constituting radiolarian ooze (Chapter IX.). 
The third order, Foraminifera, also consists of a vast assemblage 
of small pelagic organisms. They usually have a shell, made of 
calcareous, arenaceous or chitinous material. It is often chambered, 
