GELATINOSI. 515 



swim, crawl, and even walk by alternately fixing their two extremities in 

 the manner of Leeches or of the caterpillars called Geometrse. They agi- 

 tate their tentacula and use them for seizing their prey, which can be seen 

 being digested in the cavity of their body. They are sensible to the action 

 of lig'ht, and seek it, but their most wonderful property is that of being con- 

 stantly reproduced bj' the indefinite excision of their parts, so that we can 

 multiply them at will by means of division. Their natural increase is by 

 shoots which push out from various points of the body of the adult, and at 

 first resemble branches. 



There are several other genera belonging to this order, such as Corine, 

 Vorticellay &c. 



ORDER III. 

 CORALLIFERI. 



The Coralliferi constitute that numerous suite of species which 

 were long considered as marine plants, and of which the individuals 

 are in fact united in great numbers to constitute compound animals, 

 mostly fixed like plants, either forming a stem or simple expansions, 

 by means of a solid internal substance. The individual animals, 

 more or less analogous to the Actinije or Hydras, are all connected 

 by a common body, and are nourished in common, so that what is 

 eaten by one goes to the nutrition of the general body, and of all 

 the other Polypi. Their volition is even in common, at least it is 

 certainly so in the free species, such as the Pennatulae, which are 

 seen swimming by the contractions of their stems, and the combined 

 motions of their Polypi. 



The name of Coral has been given to the common parts of these 

 compound animals; it is always formed by deposition, and in layers 

 like the ivory of teeth, but is sometimes on the surface, and some- 

 times in the interior of the compound animal. This difference of 

 position has given rise to the following families. 



FAMILY I. 



TUBULARII. 



Those of the first inhabit tubes of which the common gelatinous 

 body traverses the axis, like the medulla of a tree, and that are 



