CQILENTERATA 
HE animals included in the phylum Celenterata were once all 
called zodphytes, or animal plants, because of their resem- 
blance to vegetable forms. The name Celenterata is derived 
from two Greek words meaning “ hollow” and “intestine,” and 
it describes the anatomical structure of each member of the 
group. They are commonly known as polyps. In the simplest 
forms the parts which perform the different functions cannot be 
distinguished one from the other, and even in higher forms there 
is but little differentiation. Shakspere’s description of old age 
applies to them: “Sans teeth, sans eyes, sans taste, sans every- 
thing.” 
Nevertheless, this very low order of animals has, like the 
higher orders, such a diversity of form and habit as to require 
classification. Some of them are stationary, and of these some 
branch like plants; some move about by the aid of tentacles, some 
move by means of vibrating cilia, and others move by the con- 
traction and expansion of the soft: body. 
Cuvier included them in his Radiata, a class comprising all the 
animals whose parts diverge or radiate from a central axis. 
Recent classification has divided the radiate animals into several 
classes. This arrangement of parts is obviously quite different 
from that of bilateral symmetry, or the disposal of parts on each 
side of a longitudinal axis. The type of radiate structure is 
shown in polyps. The body is a sac, in the center of which is 
another sac or axis. This is the digestive cavity. Vertical 
partitions extend from the central to the outer sac, forming dis- 
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