CLASS ACTINOZOA 
SEA-ANEMONES, REEF-CORALS, SEA-FANS, SEA-WHIPS, AND SEA-PENS 
HE animals of this class are divided into two subclasses, 
based on the following anatomical differences: In the first 
subdivision, which includes the sea-anemones and the reef-build- 
ing corals, the polyps have numerous simple, hollow tentacles and 
radial partitions of the same number, both being some multiple 
of six. The polyps of a colony are all alike, and the hard matter 
they secrete is carbonate of lime. In the second subdivision, 
the Alcyonaria,—or haleyonoids, as they are commonly called,— 
the tentacles and radial partitions are always eight in number, 
and the tentacles have small symmetrical appendages or branches. 
The polyps of this group are often accompanied by small zodids 
having no tentacles. The hard secretions are horny and elastic, 
as in sea-fans, sea-whips, and sea-pens, or they are extremely hard, 
as in Corallina rubrum. 
SUBCLASS ZOANTHARIA 
(‘‘ Animal-flowers”"’) 
ORDER ACTINIARIA 
SEA-ANEMONES 
These curious and, at times, beautiful creatures are polyps, and 
are constructed on the radial system. They havea cylindrical body 
with a broad base and rows of hollow tentacles around the upper 
disk. They have a central sac, and a space between the outer and 
inner sacs which is divided vertically by walls called mesenteries, 
as explained on page 114. Each tentacle, however many there 
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