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 calcare- 

 ous crust or bark. In dried specimens this becomes very brittle 

 and is easily broken from the horny axis. (Plates XL VI, XL VII.) 



The sea-fan& 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- 



