CLASS V. POLYPI. 



635 



fleet as this, seen with the sun shining strongly upon them, is a magnificent spectacle, from 

 " the beautiful iridescence with which the sunlitrht is 



reflected to the eye of the beholder. With the ap- 

 proach of night this scene of beauty only gives place 

 to another ; for these Medusa) are exceedingly lumi- 

 nous in the dark. 



The Medusa aurita, Pelagia Labiche^ and Cyancea 

 capillata, which we have ah'eady noticed, belong to 

 this order, as well as a multitude of others. 



ORDER 2. GYMNOPHTHALMATA. 



This order includes a great number of genera, the 

 species of which vary exceedingly in form and size- 

 Several species are found in the European seas, and 

 among them the Sarsice and Z2222«, some of which we 

 have mentioned ; also those of the genus Thauman- 

 tias, which are most important agents in producing the 

 luminosity which is often witnessed in those parts of 

 the ocean. The Oceanidce are among the most delicate and beautiful of the order, consisting of 

 a conical or globular glassy body, within which a variously colored peduncle may be seen. In 

 the genus Turris the tentacles are exceedingly numerous, while in Saphenia they are reduced to 

 two. In the Willstdce, the radiating vessels, six in number, are curiously forked, and there are 

 six ovaries placed round the base of the stomach. The ^quoridce include some of the largest 

 of the naked-eyed Medusa). 



THE EHIZOSTOMA CUVIEEI. 



0^^,^ 



Class V. P01,YPI. 



This class, deriving its name from the Greek, polus^ many, and jooms, a foot, includes a great num- 

 ber of animals, bearing the various names of Sea-Anemones^ Corals, Madrepores, Zoopliijtes, Coral- 

 lines, &c. Most of them are of very simple construction. They are all aquatic in their mode of life, 



and by far the greater number inhabit the sea, a 

 very few only being found in fresh water. Most of 

 them live in societies of greater or less extent, sup- 

 ported on a common stock, or polypklom, a word 

 which means the House of the Polypi, this being 

 sometimes horny, sometimes calcareous. The little 

 creatures are either imbedded in cavities, formed im- 

 WenM mediately in the substance of this support, or in a sort 

 of flesh which sometimes nicrusts it; or they are iii- 

 '' closed, as in tlie horny polypidoms, in minute cups 

 or tubes, from which the body can be protruded at 

 pleasure, and again retracted at the approach of 

 danger, or during repose. These social polypi are 

 always of small size, although the structures pro- 

 duced by the united labors of successive multitudes, 

 are often sufiicient to produce important changes even 

 in the face of nature. Many of the solitary species, 

 however, attain a considerable magnitude. The 

 bodies of these animals are generally cylindrical in 

 form, with a fringe of tentacles, or arms, frequently consisting of a considerable number, sur- 

 rounding the anterior extremity, in the center of which the mouth is situated. The mouth is 







POLTPIDOM OF TREE-CORAL. 



