6o Animal Life by the Sea-shore. 



alimentary tube with rnoutli and vent, the former being sur- 

 rounded by a crown of tentacles. This comparatively high 

 organisation of the individual animals distinguishes the Polj'zoa 

 from the Hydroid Zoophytes, with which they are often 

 confounded, and which will be described in the last chapter. The 

 Sea-mat is the most conspicuous of our Pol5'zoa on account 

 of the frequency with which tlie dried colonies are washed 

 ashore ; examination of rock- pools will, however, disclose 

 many other forms, some of which are most delicately branched. 

 In some members of the group the colonies are not ramified but 

 as, for instance in the Lace-coralline, Memhranipora 



FIG. 74. SEA-MAT (fLUSTRA FOLIACEA). 



pilosa, which frequently covers seaweeds with the most delicate 

 lace-like tracery. 



Having thus briefly reviewed the principal worms and their 

 allies which are large enough to attract attention, we pass on 

 to other forms which differ bj' the lack of bilateral symmetry, 

 at least in their more typical representatives. 



