104 CORALS AND CORAL ISLANDS. 
face, and are always without any prominent calicles, there 
being only very minute rounded punctures over the surface, 
from which the animals show themselves. The cells in the 
corallum are divided parallel to the surface, but irregularly, 
by very thin plates or tables, approaching in this character 
the Pocilliporee and Favosites. 
Each coral is a group or colony of Hydroids in the Hydri- 
form state. Agassiz observes that the animals of Millepora 
are very slow in expanding themselves. When expanded, they 
have no resemblance to true polyps; there is simply a fleshy 

ANIMALS OF MILLEPORA ALCICORNIS, MUCH ENLARGED. 
tube with a mouth at top and a few small rounded promi- 
nences in place of tentacles, four of them sometimes largest. 
The preceding figure, from Agassiz, shows, much enlarged, a 
portion of a branch of the AMillepora alcicornis with the ani- 
mals expanded; and the small figure a, near the top of the 
cut, gives the natural size of the same. But it has been fur- 
ther observed by Moseley that in the Millepores the animals 
have two forms: one is the tentacle-like kind here figured, 
and the other shorter and mouth-bearing; and the former 
are sometimes arranged around the latter in more or less 
perfectly circular groups, called “ cyclosystems.” 
