86 CORALS AND CORAL ISLANDS. 



of slender twigs, and others like many-branched shrubs or 

 miniature trees. 



The exterior of the stem or branch in a Gorgoma is a 

 layer of united polyps, with minute calcareous spicules dis- 

 tributed through the tissues and giving the layer some firm- 

 ness. It is like a bark to the axis of the stem or branch, and may 

 be peeled off without difficulty, and hence is often called the 

 cortex. The outer surface of the dried cortex is often smooth, 

 or nearly so ; but sometimes covered with small prominences. 

 Over it there may be seen numerous oblong points (one to 

 each of the prominences if there are any ; each of these is 

 the spot where a polyp opened out its tentacles when the zoo- 

 phyte was alive. 



Kolliker and others have shown that genera, and some- 

 times species, of the Gorgonacea, may be distinguished by the 



SPICULES OF GORGONI^E, MUCH ENLARGED. 



forms of the calcareous spicules. Some of these knobby spi- 

 cules are represented in the annexed cut, from figures published 

 by Prof. Verrill. The most common forms are those of figures 

 1, 4, 5 ; they occur, with small differences, in the genera Gor- 

 gonia, Eugorgia, Leptogorgia, etc. Figure 1 is from the Lep- 

 togorgia eximia V. Figure 2, in which one side is smooth 

 (from the Gorgoma quercifolia V), is characteristic of the 

 genus Gorgonia, but occurs in the species along with forms 

 much like fig. 1. The forms represented in figures 3, 4, 5, 



