142 HALF AN HOUR WITH SEA-MATS AND SQUIRTS. 



carbonate of lime to strengthen them. The cham- 

 bers have each a small semicircular aperture, in 

 which the animal formerly lived, and out of which 

 it could thrust its tentacles or cilia. The scientific 

 name given to this group is Potyzoa, or " many 

 creatures ;" sometimes we find them called Bryozoa, 

 or " moss-like animals." Singularly enough, these 

 apparently insignificant creatures are nearly allied 

 to shell-fish, and are much more highly organized 

 than the corallines, with which they were formerly 

 classed on account of both having a horny or 

 chitinous framework. The distinction between the 

 two classes is very great, and especially in their 

 internal structure. In the corallines, already dwelt 

 upon, we have shown that all the individuals are 

 united by a common flesh, scientifically termed 

 coenosare. The latter, however, is only a technical 

 Greek word signifying the same thing. In the 

 sea-mats, on the contrary, the connection is merely 

 an external one, and the various species rarely are 

 connected in any other manner. A distinct and 

 separate animal lives in each net-like chamber, and 

 has no connection with its neighbour except that of 

 simple contact. In spite of this distinctive fact, 

 the entire colony has in every case been developed 

 from a single individual. To distinguish the indi- 

 viduals of a colony, like those of the sea-mat in 

 Fig. 71, the name of Polypide has been given them, 

 Polypite being the technical name of each member 

 of the colony in the sea-firs, or corallines. 



