252 COMPARATIVE ZOOLOGY. 
lar matter; and the most conspicuous signs of life are the 
contraction and lengthening of the worm-like body. They 
feed by absorption, and are all parasites, living in the ali- 
Fig. 179.—Gregarina gigantea, highly magnified: a, nucleus. 
mentary canal of higher animals; particularly in the Cock- 
roach and Earth-worm. The name is derived from the 
fact that they occur in large numbers crowded together. 
By some authors they are associated with the parasitic 
Worms. 
Crass 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 Ame- 
ba, Foraminifera, and Polycystina. 
An Ameeba 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 contractile cavity inside. 
It has no particular form, as 
it changes continually. It 
moves by putting forth short, 
| blunt processes, and eats by 
Fig. 180.—Ameba princeps, X 150; the wrapping its body around the 
same animal in various shapes. particle of food. The size 
ranges from 7; to z25y of an inch in diameter. Speci- 
mens can be obtained by scraping the mucous matter 
from the stems and leaves in stagnant ponds. 
