CORALS. 
5°9 
seemed to become exhausted, contracted, and became attached. The transition 
from the worm-like larva to the polyp takes place as in the anemones. The 
thicker end of the body is pressed against a hard rock, and the whole contracts 
into a thick, round disc; while longitudinal furrows become visible at the upper 
pole, where the mouth sinks deeper. At the ends of these furrows the twelve 
tentacles appear. The accompanying three illustrations show the stages which 
developmental stages Of Astroides calyculavis (magnified 24 times). 
follow in rapid succession, resulting in a form almost exactly like a young sea- 
anemone. It has, however, already commenced to secrete its calcareous skeleton. 
This is not formed as a connected whole, but begins as a number of separate centres 
of secretion between the polyp and the substance to which it is fixed. These meet 
and fuse, till gradually the skeleton is produced. The polyp commences to bud,, 
and the buds develop their skeletons, the whole together forming a stock like that 
shown in the illustration. 
The star-corals, which are some of the principal reef-builders, do not branch, 
but form great solid mounds; 
the polyps being all cemented 
together, and the budding so 
arranged that the whole colony 
forms a thin, living layer or 
covering to the mass it and its 
parents have built up; all but 
this thin layer on the surface 
being dead coral. The illustra¬ 
tion given is of A.strcea pallida, 
a species which appears as a 
rounded mass, with flat base, and 
the individuals being quite dis¬ 
tinct from one another, although their outer walls are in contact. Those on 
the top and to the right of the figure are represented in a contracted condition, 
and the rest with expanded tentacles. None of the individuals here seen are in 
the act of dividing; and the genus is characterised by the fact that the bud- 
