AGE OF CORAL REEFS. 193 
periority of the single ones and of those that 
grow in communities. When the little Polyp 
Coral, the Astraan or Madrepore, for instance, is 
born from the egg, it is as free as the Actinia, 
which remains free all its life. It is only at a 
later period, as its development goes on, that it 
becomes solidly attached to the ground, and be- 
gins its compound life by putting forth new 
beings like itself as buds from its side. Since 
we cannot suppose that the normal development 
of any being can have a retrograde action, we 
are justified in believing that the loss of freedom 
is in fact a stage of progress in these lower 
animals, and their more intimate dependence on 
each other a sign of maturity. 
There are, however, structural features by 
which the relative superiority of these animals 
may be determined. In proportion as the num- 
ber of their parts is limited and permanent, their 
structure is more complicated ; and the indefi- 
nite multiplication of identical parts is connected 
with inferiority of structure. Now in these low- 
est Polyps, the Actinia, the tentacles increase 
with age indefinitely, never ceasing to grow while 
life lasts, new chambers being constantly added 
to correspond with them, till it becomes impossi- 
ble to count their numbers. Next to these come 
the true Fungide. They are also single, and, 
though they are stony Corals, they have no share 
9 M 
