18 



ON POLYPS. 



luxuriant verdure, and peoples with appropriate inhabitants. Va- 

 rious indeed are the forms which these creatures offer to the zoolo- 

 gist ; and the classification of them, even at the present day, is a 

 subject of much doubt and uncertainty. Without entering fur- 

 ther into the subject of their division into groups and families 

 than is connected with our purpose of examining the main features 

 of their economy, we shall select some of the most marked varieties 

 for description, commencing with the simplest and least elabo- 

 rately formed. 



(21.) We have already seen that in the Sponges the living portion 

 of the animal was composed of a gelatinous film, which, without any 

 apparent organization, was possessed of the power of extracting nutri- 

 ment from the water around it, of deriving from the same source ani- 

 malized materials and earthy particles, which were deposited within 

 its texture, and used in constructing a porous frame-work or skele- 

 ton ; and, moreover, that the same semifluid parenchyma could de- 

 velope from its substance germs, which became ultimately expanded 

 into other beings resembling that from which they sprung ; we shall 

 therefore be prepared to find, in the class upon which we are enter- 

 ing, like results produced by equally simple means. 



Among the calcareous 

 structures, derived from 

 the tropical seas, which 

 are usually known by the 

 general terms of Madre- 

 pores, Corals, &c. and 

 which, from the beauty of 

 their structure, form the 

 ornaments of our cabinets, 

 few are more common than 

 those denominated Fun- 

 gise and Meandrinse, 

 animals belonging to the 

 group Madrephyllicea of 

 systematic zoologists. 



These masses consist of thin plates or laminse of various dimensions 

 (fig. 3.) disposed in different directions in different species, but in 

 the Fungia Agariciformis, which we have selected as an example, 

 radiating from a common centre, and forming a circular mass resem- 

 bling a mushroom. When living in its native element, every part of 

 the surface of this stony skeleton was encrusted with a film of animal 



Fig. 3. 



