SECT. IT. GORGONIID^E. 123 



supply their juices with oxygen, and carry off the car- 

 bonic acid gas and refuse of the food. In this case, as 

 in many others, the cilia may be regarded as respiratory 

 organs. 



The unarmed Alcyons are generally thick, short, and 

 rough ; some form a crust on rocks from whence lobes 

 rise. With the exception of the Xenia, a tropical species, 

 the polypes of the unarmed Alcyons can retreat within 

 their polypary, so as to be entirely or partially out of 

 sight. 



The polypary, or mass, of the armed Alcyons is either 

 membranous or leathery, and is entirely bristled with 

 large spicules similar to the very small ones in the 

 tentacles of its polypes. It forms branching masses 

 terminated by prominent tubercules thickly beset by 

 spicules. The polypes retreat into the mass when they 

 are in a state of contraction. 



The Gorgons, which form the second family of Al- 

 cyonian zoophytes, are compound animals, consisting of 

 a solid stem or axis either simple or branched, adher- 

 ing by its base to a rock or some submarine body, and 

 coated by a layer of a softer fleshy or horny substance 

 exactly in the same manner as the bark covers the stem 

 and branches of a tree. This bark or fleshy substance 

 is filled with polypes similar to those described: however, 

 they are shorter, their base is a little enlarged, and is 

 turned towards the axis of the stem and branches of the 

 Gorgon. The softer substance or bark is much de- 

 veloped between the polypes, and is fall of spicules, of 

 forms varying with the genera. A system of almost 

 capillary canals traverses the soft coating and opens 

 into the lower part of the cavity containing the viscera 

 of the different individuals, thus affording a passage for 

 the circulation of the nutritive juices. 



The larvae of the Gorgons are like ciliated eggs ; they 

 swim with their thick end foremost, and are perfectly soft. 



