38 James D. Dana, Esq., on the Structure^ 



often as broad as the disk itself, and usually not much longer, 

 which contains the stomach and internal cavity of the polyp ; 

 and the mouth, which opens into the stomach, is placed at 

 the centre of the disk. Here, then, the flower animal and 

 the garden-flower diverge in character, the difference being 

 required by the diff'erent modes of nutrition in the two king- 

 doms of nature. 



There are many species of polyps, which have all the ex- 

 ternal and internal characters of coral polyps, yet secrete no 

 lime or coral. Our descriptions of structure may be best 

 drawn from them, and afterwards the single peculiarity of 

 the coral-making polyp — ^its secretion of coral — will come 

 under consideration. The species here referred to are called 

 Actinioe in science, in allusion to the radiated or aster-like 

 flower which forms the summit of the animal.* There is the 

 same allusion in the common appellation Sea Anemone. The 

 richest anemones, daisies, and tulips of our gardens would 

 not rival them in beauty, neither will they exceed them in the 

 size of their flowers ; for a breadth of two and three inches 

 is common. The polyps here alluded to, along with the coral 

 polyps allied, constitute the order or division of zoophytes 

 called Actinoidea.t 



The Actiniae are entirely fleshy, and usually live attached 

 by their lower extremity to the submerged rocks of the shores. 

 The mouth, at the centre of the flower-like disk forming the 

 summit of the animal, is a simple opening without teeth or 

 appendages of any kind. The tentacles — ^the petals of the 

 flower — are tubular organs, and communicate internally with 

 the interior cavity of the animal. The animal contracts when 

 disturbed, and conceals the flower by rolling inward over it, 

 the margin bearing the tentacles ; and in this state it seems 

 like a lifeless lump of animal matter. Left quiet for a while, 

 it again expands and appears as before. This expansion is 

 produced by receiving water into the interior from without, 

 mostly through the mouth, and thus filling the tentacles and 

 swelling out its fleshy body. They are generally found ex- 



* From a,')(TlVj « ray of the sun. 



t This term alludes to their general resemblance to Actinias. 



