240 
COMPARATIVE ZOOLOGY. 
the essential signs of life. The usual methods of repro¬ 
duction are self-division and budding. 
The subkingdom may be divided into four classes: Mo¬ 
nera , Rhizopoda , Gregcirinida , and Infusoria . 
Class I.—Monera. 
These simplest living beings are organless 
bits of protoplasma, with no distinction of lay¬ 
ers, and so far as observed not even a nucleus 
is present. They are round when at rest, and 
have pseudopodia when active. They are all 
aquatic, and some are parasitic. Such is Pro- 
tamoeba, Fig. 183. 
Fig. 188.— Pro- 
tamoeba pri¬ 
mitivei. 
Class II. —Rhizopoda. 
The Rhizopods are characterized by the power of throw¬ 
ing out at will delicate processes of their bodies, called 
pseudopodia , or false feet, for prehension or locomotion. 
They possess no cilia. The representative forms are Amoe¬ 
bae, Foraminifera , and Radiolaria. 
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 rather distinct layers, and 
has a nucleus and a contractile 
cavity 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, 
from T V to ybVo of an inch in diameter, 
Fig. 134.— Amoeba princeps, X 150; the 
same animal in various shapes. 
The size ranges 
To - L,J innnr U1 aL1 in uiamcici. Specimens can 
be obtained by scraping the slimy matter from the stems 
and leaves in stagnant ponds. 
