152 MARINE INVERTEBRATES 
one another, but connected by horizontal platforms at short in- 
tervals. The form of reproduction, by budding, in this colony is 
peculiar to itself. The spicules of lime secreted in the polyp 
unite or fuse into a tube or cylindrical skeleton. At certain 
stages of development the polyp sends out a horizontal expan- 
sion, which unites with the expansions of other polyps and be- 
comes calcified, forming a shelf which binds the tubes together. 
From the top of the platforms other corallites are formed, and 
thus a colony is made, which broadens as it rises in its growth. 
The body of the polyp is green, the skeleton red. It belongs to 
the East Indian seas and is given here only as an example of a 
peculiar manner of growth. 
ORDER GORGONACEA 
SEA-FANS, SEA-WHIPS, AND SEA-FEATHERS 
These are compound, tree-like Alcyonaria, with a calcareous or 
horny skeleton which forms a branched axis and is covered with a 
layer of united polyps having spicules of lime distributed through 
the mass, which give some firmness to the bark-like covering. 
Gorgonias, in great variety, grow in abundance on the coral reefs 
and mud-flats of Florida, forming masses of low shrubbery, pink, 
yellow, brown, or purple in color. 
The sea-whips and sea-feathers are varieties of gorgonias, 
which are named from their forms. Some have shapes which 
resemble branching shrubs; others are long unbranched rods, 
either straight or spiral. They attain a height of several feet and 
are of various colors. The colony has a horny axis surrounded 
by a living mass which resembles a sheet of animal matter. This 
mass consists of polyps closely united, and has throughout its sub- 
stance spicules of carbonate of lime, making it a kind of caleare- 
ous crust or bark. In dried specimens this becomes very brittle 
and is easily broken from the horny axis. (Plates XLVI, XLVIL) 
The sea-fant are colonies with a central, horny, flexible, and 
much-branched axis, covered, as in the sea-whips, with a layer of 
united polyps containing spicules of lime, which make a some- 
