518 RADIATES: POLYPS. 



ters. They vary in size from microscopic forms to sev- 

 eral inches, and even a foot or more, in diameter. Some 

 are wholly soft, others secrete more or less solid parts. 

 In this respect there is every grade, from those wholly 

 fleshy to those which secrete a solid framework. This 

 framework is called Coral* The top common notion 

 that coral is built by an insect, or that the coral ani- 

 mals build coral at will, as the bee builds comb, or as 

 workmen masonry, is wholly erroneous. Coral is sim- 

 ply the framework or skeleton, or aggregate skeletons, 

 of polyps, or, in some cases, as we have seen, of aca- 

 lephs, and is a necessary result of their existence, and 

 is entirely independent of the volition of the animals 

 themselves. In fact, polyps form coral in a manner 

 not different in kind from that in which the higher ani- 

 mals form bones ; and the coral is wholly inside the pol- 

 yps, and is in no sense a house, as is too commonly sup- 

 posed, in which the latter live ; and it is only when the 

 polyps die, wither, and disappear that we see the solid 

 coral itself. From their resemblance to plants, the ani- 

 mals of this class were regarded by the early naturalists 

 as vegetable forms ; and later they have been regarded 

 as partaking of the nature of both plants and animals ; 

 but now their strictly animal character is established be- 

 yond any question. Still, they are often called Zoophytes, 

 as well as Polyps. The forms and hues exhibited by 

 them are almost endless. Some parts of the tropical 

 seas, where polyps especially flourish, rival in graceful 

 and varied forms, and in beauty and splendor of colors, 

 the most beautiful flower-gardens of the land. There is 

 scarcely a form of vegetation, either trunk or branch, leaf 

 or flower, fern, moss, lichen, or fungus, that is not imi- 

 tated with striking exactness by these wonderful animals 

 of the sea. 



* Corallum is the term used by Dana in his most excellent works on 

 Zoophytes. 



