146 THE SIMPLEST ANIMALS — PROTOZOA 
118. Paramecium. — One of the most common forms of 
Protozoa is the slipper-shaped Paramecium (para-me'- 
shi-um), which is more active than the amoeba. It is 
abundant in stagnant water and in the hay infusions pre¬ 
pared in the laboratory. (See Laboratory Suggestions.) 
LABORATORY STUDY 
There are certain kinds of Protozoa that are usually found in pro¬ 
tozoan cultures. The most abundant form is the paramecium. Make 
repeated examinations of drops of water from the protozoan culture, 
until you are able to find the 
paramecium. Notice its 
shape, rate of movement, be¬ 
havior on meeting obstacles, 
and the like. Report on what 
you can make out. Compare 
the paramecium with any 
other protozoon you can find, 
as to shape, rate of movement, 
size, color, etc. If available, 
examine slides which show the 
nucleus of a protozoon. Make 
sketches that illustrate the 
above features. 
Structure of Parame¬ 
cium .—The paramecium, 
like the amoeba, is a single 
cell, but it has both a large nucleus and a small one. It 
has an endoplasm, an ectoplasm, and a cuticle (ku'ti-kl), or 
cell wall. Through the cuticle there extend great numbers 
of cilia (sil'i-a), or threads of living protoplasm. The ecto¬ 
plasm contains many thread-like darts known as trichocysts 
(trik'o-sists). These can be discharged. Within the cell are 
found food and water vacuoles as in the amoeba; but there 
are two contractile vacuoles, one at either end, and the 
food and water vacuoles are more numerous than in amoeba. 
119. Locomotion and Defense. — The, animal moves by 
