THE COMMON SEA MAT. 595 



of the lemon-peeL Their origin, however, is of an animal and 

 not a vegetable nature, for they are the submarine houses of a 

 vast class of animals technically called Polyzoa, because many 

 distinct animals are associated together in one community. 



For many years their place in the scale of creation was 

 extremely dubious, but they are now acknowledged to be allied 

 to the molluscs, and to be really of a higher nature than the 

 bright and active insects. In general form they so resemble 

 the zoophytes, that the two great groups have been confused 

 together, although they are in reality farther apart than the 

 monkey and the snail They assume various forms, which may 

 be reduced to three, namely, a flat, leaf-like shape, a form as of 

 delicate branching twigs, and a flat series of cells spreading over 

 other substances, such as the stem or frond of a sea-weed, an 

 empty shell, or submerged plant, and similar objects. 



The most familiar of these Polyzoa is the common Sea Mat, 

 which has already been mentioned, and which is called by the 

 scientific name of Flustra Foliaeea. If the finger be passed over 

 one of these leaf-like objects, a decided roughness is felt, like 

 the surface of a file, and if it be drawn through the hand from 

 base to tip, the roughness becomes so marked that the leaf can 

 hardly pass. The reason for this roughness may be seen by 

 reference to Fig. 12, which is a magnified representation of a 

 part of the same object. It will be seen that the Flustra is 

 composed of a vast number of cells, each cell being furnished 

 with little tooth-Kke projections, which produce the roughness 

 already mentioned. 



The cells are formed by their inhabitants, and very much 

 resemble in outward form the polypi which fill the cells of the 

 zoophytes, each of which possesses a beautiful plume of tentacles, 

 as is seen in the uppermost cell. When the animals are at 

 rest they are withdrawn so closely into their cells that they can- 

 not be seen ; but when they are hungry and desii'ous of feeding, 

 they push themselves out of their houses, like so many snails 

 out of their shells, expand their beautiful plumes, and await the 

 food which is brought to them by the action of the water. 

 Under the microscopes they are lovely objects, and even when 

 they are dead their empty habitations are full of beauty. 



A detailed description of all the species which are represented 

 in the illustration would occupy too much space, even if it were 



QQ2 



