WORMS. 



189 



fresh water, but in the warmer parts of the Old World land 

 leeches cccur in the moist forests, and these form almost 

 intolerable pests. 



CLASS IY.--MOLLUSCOIDEA. 



Under this heading are grouped a few forms, which in 

 time past were considered as Molluscs (see p. 193), but 

 which are now known to have only superficial resem- 

 blances to the clams, etc. There are two orders of these 

 Molluscoids. 



ORDER I. POLYZOA (Moss Animals). 



The Polyzoa are individually small, but by budding 

 they form colonies of considerable size, the tentacles of 

 the individuals giving the colony a mossy appearance, 

 whence the name Bryozoa (moss animals) often given them. 



FIG. 32. Diagram of a Brachiopod. 6, tentacles around mouth, m* i, intes- 

 tine; the shell black, the stalk to the right. 



These tentacles surround the mouth in a more or less modi- 

 fied circle, and by them the animals obtain their food. 

 The body is sac-like, and the alimentary canal is bent upon 

 itself so that the vent is near the mouth. Many of the 

 colonies secrete an external skeleton, which may be horny 

 or calcareous. Most of the Polyzoa are marine, but a 

 few occur in fresh water. 



