PROTOZOA OR SIMPLEST ANIMALS. 
3 
Food may be taken in and the remains ejected at any point of High Wall 
the body, but sometimes only over more or less definite areas. The g as ® nd of 
body of the animal is usually crowded with food-balls, shells of Gallery. 
Diatoms, cells of green algae, &c. 
The protoplasm of the body, with the exception of a thin, clear, 
outer layer, is granular ; at one part (Fig. 1) is seen a discoid, denser 
portion of protoplasm, known as the “nucleus.” There is also 
present in the interior of the body a clear spherical vesicle — the 
“ contractile vacuole ” — which slowly expands and rather suddenly 
collapses and disappears, reappearing at the same spot and going 
through the same cycle. The contractile vacuole is probably an 
organ for the excretion of waste products. The animal reproduces 
itself by dividing into two, this process being preceded by division of 
the nucleus, each half of the Amwba becoming a distinct individual. 
Classification. 
The Protozoa are divided into two great sections — the Gymno- 
myxa or Ehizopoda, and the Corticata or Infusoria. 
In the first section, the protoplasm of the cell is homogeneous 
throughout, but in the second the superficial layer is firmer than 
the more fluid interior portion. 
The Gymnomyxa, in their adult phase, move about and obtain 
their prey by means of pseudopods. The Corticata are provided 
with flagella or cilia. A classification of the Protozoa (after Prof. 
Lankester, Encyc. Britannica ) is given in the “ Explanation of 
Plates ” in the Case. 
GYMNOMYXA (RHIZOPODA). 
For simplification, the Gymnomyxa are here divided into four 
groups : — 
I. Lobosa, with lobose pseudopods. 
II. Heliozoa, with fine radiating pseudopods. 
III. Foraminifera, in which main trunks of pseudopods branch 
out into a fine network, and with a shell usually composed of carbonate 
of lime. 
IV. Radiolaria, with a “ central capsule,” with fine radiating 
pseudopods, and usually with a shell of silex or horny acanthin. 
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