OMNIVOROUS ANNELIDS, &c. 



261 



fixed forms commonly get their living by setting up currents in 

 the surrounding water. In this case the current-producing organs 

 are two often complicated "arms", fringed outgrowths from the 

 mouth-region richly covered with cilia, the movement of which 

 produces food-bearing streams of sea-water, which are conducted 

 along grooves to the mouth. All Brachiopods are marine, and 

 at the present time they exist in greatly-diminished numbers, 

 though in older geological epochs they were dominant forms of 

 marine life. 



MOSS -POLYPES (POLYZOA) 



The Moss-Polypes are small animals, nearly always fixed, 

 and in most cases living in colonies produced by budding (vol. i, 

 pp. 436-438). Most of them are marine, but several kinds are 

 inhabitants of fresh water. A great many species are found 



Fig. 469. — Moss-Polypes (enlarged) 

 A, Small colony of Lophopus crystaliiiuis, showing some individuals fully extended, and 

 others in different states of retraction. B, Diagram of a single individual oi Plujuatella, cut 

 through centre of body. 



attached to sea-weeds, &c., alono- the British coasts, and there 

 are also some native species in our streams and lakes. The 

 projecting end of each individual bears both openings of the 

 U-shaped gut, and also a crown of ciliated tentacles (lophophore) 

 which has been compared to the "arms" of the preceding group, 

 and which has at any rate the same chief function, the setting up 

 of food-bearing currents in the surrounding water (fig. 469). 



WHEEL-ANIMALCULES (Rotifera) 



These minute creatures mostly live in fresh water, including 

 puddles, roof-gutters, and the moisture saturating damp vege- 



