CHAPTER II 
PROTOZOA 
CHARACTERISTICS.— Unicellular, or uf composed of more than 
one cell, such elements not arranged in tissues. Food ingested 
by a special mouth or by any part of the cell substance. 
Reproduction never takes place by ova and spermatozoa. Some 
forms are colonial. 
Group A. GYMNOMYXA. 
The Protozoa have been divided into two groups, the 
Gymnomyxa, corresponding with the old group Rhizopoda ; 
and the Corticata, which comprise the Infusoria and Gregarin- 
idea. The former group includes all those forms which, like 
Amoeba, have, during the dominant phase of their life-history, 
no limiting membrane. Their protoplasm is consequently 
exposed, at any rate at one portion of their surface, and tends 
to run into processes or pseudopodia, which vary in appearance 
in the different species. Food may generally be ingested at 
any point of the naked protoplasm. 
Although the amoeboid condition is the one in which 
these organisms most frequently occur, they may pass through 
other phases, such as rounded spores enclosed in a membrane 
(chlamydospore), naked spores with a lash-shaped pseudopodium 
(flagellula), etc. Not infrequently two or more individuals 
fuse together, and this fusion may be the precursor of repro- 
duction. When the bodies of numerous amoebiform indi- 
viduals run together to form a large mass of protoplasm, the 
result is known as a Plasmodium. 
