PKOTOZOA. 
241 
They possess no cilia. The representative forms are Amosr 
bee, Foraminifer a, and Polycystina. 
An Amoeba is a naked fresh-water Rhizopod; an in¬ 
definite bit of protoplasm, as structureless as a speck of 
jelly, save that it is made of 
two distinct layers, and has a 
nucleus and a contractile cav¬ 
ity inside. It thus differs 
from the Monera. It has no 
particular form, as it changes 
continually. It moves by put¬ 
ting forth short, blunt proc¬ 
esses, and eats by wrapping 
its body around the particle of food. The size ranges 
from -Jg- to -g feVo of an inch in diameter. Specimens can 
be obtained by scraping the mucous matter from the 
stems and leaves in stagnant ponds. 
A Foraminifer differs from an Amoeba in having an 
apparently simpler body, the protoplasm being without 
layers or cavity; its pseudopodia are long and thread-like, 
and may unite where they touch each other. It has the 
property of secreting an envelope, usually of carbonate of 
Fig. 1S5 .—Aviceba princeps, X 150; the 
same animal in various shapes. 
Fig. 186.—Rhizopods: a, a monothalamous, or single-chambered, Foraminifer (Lo- 
gena striata ); 6, a polythalamous, or many-chambered, Foraminifer (Polystomella 
crispa), with pseudopodia extended; c, a Radiolarian, one of the Polycystines 
(PodoeyrtU Schomburgkii ). 
16 
