FORMATION OF CORAL REEFS. 163 
lime does not belong either to the naturalist or 
the geologist, its suggestion reminds us that the 
time has come when all the sciences and their 
results are so intimately connected that no one 
can be carried on independently of the others. 
Since the study of the rocks has revealed a 
crowded life whose records are hoarded within 
them, the work of the geologist and the natural- 
ist has become one and the same, and at that 
border-land where the first-crust of the earth was 
condensed out of the igneous mass of materials 
which formed its earliest condition, their investi- 
gation mingles with that of the astronomer, and 
we cannot trace the limestone in a little Coral 
without going back to the creation of our solar 
system, when the worlds that compose it were 
thrown off from a central mass in a gaseous 
condition. 
When the Coral has become in this way per- 
meated with lime, all parts of the body are 
rigid, with the exception of the upper margin, 
the stomach, and the tentacles. The tentacles 
are soft and waving, projected or drawn in at 
will; they retain their flexible character through 
life, and decompose when the animal dies. For 
this reason the dried specimens of Corals preserved 
in museums do not give us the least idea of the 
living Corals, in which every one of the millions 
of beings composing such a community is crowned 
