RADIATA. 



Electra Verticillata. a Natural size. 

 b Magnified. 



Section of living S|» 



Flustra Dentata. magnified. 



or tumbling about above the substance? near it. Finally, becoming stationary, a margin gathers round the 

 body, and the centre, growing transparent, shows within an inanimate Polypus. 



Among the varieties of the Cellarisea are the Lunulitea Radiata. found in Grignon ; the Lunelite en par a- 

 sol, of Defranc; the Electra Verticillata, of Gmelin; the Flustra. Dentata, found in the northern seas; the 

 Flustra Carbasea, found in the seas of Scotland ; the Pherusa Tubuloza, of Ellis and Solander; the Cellaria 

 Ceroides, of Gmelin. found in the Mediterranean, and the Indian seas; and the Unicellaria Chelata, found 

 in the seas of North America. 



The class, Porifera, presents so complete a commixture of the characters of animals and plants, that it 

 is hard to say to which division they belong. Gn the one hand, like plants, they are fixed to one spot; 

 possessed, apparently, of no sensibility, and seem to have no power of voluntary motion. Gn the other 

 hand, their structure is unlike that of plants, and resembles that of creatures belonging to the animal 

 kingdom. They are, therefore, commonly assigned to the latter, but at the lowest point on the scale. 



The Sponge is a familiar variety of this class, which may serve to represent the whole. What we call 

 and use as Sponge is, however, but the skeleton of the creature. When alive, this fibrous network is 

 clothed, within and without, by a thin, gelatinous substance, very similar to the white of an egg. This 

 substance drains away, on the Sponge being taken from the water. During the Sponge's life, it not only 

 prows, regularly, but there is a constant flow of water in and out through its pores. These currents con- 

 vey nutriment into the interior of the mass, and carry off excretions. 



Sponges, like plants, may be multiplied by artificial division, each portion becoming a new individual. 

 Their natural mode of increase, however, is by detaching from themselves little, round, gelatinous bodies, 

 called ffemmules, which in time become counterparts of the parent. 



Some kinds of Sponges are found on almost all shores ; and some frequent deep water, whence they can 

 only be obtained by dredging. It is in this manner that the common Sponge is procured from the Medi 

 terranean, the Grecian Archipelago, and the other localities it frequents. Sponges are not confined to the 

 sea, however ; for there is a species which inhabits fresh water. 



C384) 



THE END. 



