MINERALS AND GEOLOGY OF CANADA. 507 
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Fig. 69. Fig. 70. 
Corals proper :—The animal substance of corals consists of a soft 
gelatinous mass containing one or many digestive sacks or stomachs, 
each provided at the opening or upper part with a number of retractile 
tentacles. These sacks with their tentacles are technically known as 
“polyps.” The gelatinous mass possesses likewise (in the majority of 
cases) the power of secreting amidst its tissues a calcareous or horny 
framework, the “coral” of popular language. As a general rule, this 
secreted solid portion consists of one or more cavities or cells, in and 
around which the organized fleshy sack or polyp is contained. This, 
however, is not always the case. Sometimes, as in the celebrated 
“Red (Coral” of the Mediterranean, the polyp-cavity is fashioned 
in the midst of the gelatinous matter, without any correspond- 
ing cavities in the support. When cells occur in this support or 
“corallum,” they exhibit either a round, oval, or polygonal opening ; 
and, if more than one in number, they are either in juxtaposition, or 
connected by short transverse tubes, or by a mass of more or less 
porous tissue called ‘‘coenenchyme.” The cell is sometimes smooth 
