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those SUPP 
ZOOLOG Y. 31 
from their being found in infusions. One of the most 
common of these forms is known as Paramcecium; and 
its structure will serve to illustrate this group. The Para- 
moecium (Fig. 24) is often compared to a slipper-shaped 
body of semi-fluid consistency (central substance), inclosed 
in a rind (cortical layer); the rind running insensibly into 
the semi-fluid substance. This rind is coated on its outside 
with a delicate layer (cuticula), bearing on certain parts 
hairs. (Fig. 24, ^) If the animal remain quiet, we can 
see a depression in the middle of the body, which leads 
into the so-called mouth; this opens into a kind of gullet. 
(Fig. 24, g.) This is all the digestive system the Para- 
moecium possesses. In certain parts of the body one can 
observe spaces opening and shutting (Fig. 24, c) and 
through these spaces certain canals are said to be visible, 
filled most likely with water. It is said these canals or 
vessels communicate with the exterior by means of holes in 
the layers forming the walls of the body. If such a system 
of vessels have really been found in the Infusoria (and 
many competent observers are confident that they do exist), 
they furnish an important proof of the derivation of the 
Worms from the Infusoria, as this rudimentary water-vessel 
system is much developedinthe Worms. (See Aspidogaster.) 
The hairs on the outer layer of the Paramcecium serve as 
organs of movement, and, in making currents of water, 
drag small particles of food, etc. into the body of the ani- 
mal. These hairs (Fig. 24, #) are called cilia, and their 
movement ciliary action. The Infusoria have been divided 
according to the presence or absence of these hairs into 
Ciliata and Acineta (sucking); but the transition between 
the two seems to be furnished by the bell-shaped Vorticellze, 
which are said to produce Acinete, while the Acinetz 
produce Vorticellae. If this be correct, the Acinetz are 
only a transition stage of Vorticellee, and all Infusoria are 
Ciliata or haired. 
