188 



THE SEA SHORE 



There is an interesting group of animals known collectively as 

 the Bryozoa, or Polyzoa, or, popularly, as the Moss Polyps, that 

 are often classed with the worms, though they are not, according 

 to the general idea, wormlike in appearance. They live in pretty 

 colonies, many of which are certainly familiar objects to all who 

 ramble along the sea shore. Some form pretty lacelike patches on 

 the fronds of sea weeds, while others are built up into flat, frond- 

 like, branching objects that are often mistaken for sea weeds by 

 young collectors. Among the latter is the Sea Mat (Flustra), that 

 is so commonly washed up on the shore in great abundance. An 

 examination with a lens will show that, in both instances, the mass 

 consists of very many minute cells, with horny or calcareous walls, 

 the mouth of each cell being close by an operculum. 



On placing the colony in sea water, how- 

 ever, we find that each little cell is the home 

 of a small animal, that protrudes from the 

 cell, exposing a mouth that is surrounded by 

 a crown of tentacles. A moderately high 

 magnifying power will also show that the 

 tentacles are covered with minute vibratile 

 cilia, by means of which currents of water 

 are set in motion towards the mouth to 

 supply the animal with food. Some, too, 

 have a lip by means of which the mouth 

 may be closed. 



In addition to the colonies just briefly 

 described, there are other moss polyps that 

 build up little, branching, tree-like clusters 

 which closely resemble some of the sea firs, 

 and many of these are to be found in the 



sheltered crevices of rocks, or attached to the under sides of 

 stones between the tide-marks. 



While searching the surfaces of rocks and weeds at low tide, 

 one's fingers will be constantly coming in contact with fixed, soft- 

 bodied animals that suddenly eject a fine stream of water as they 

 are touched. These are the Sea Squirts, sometimes spoken of as 

 the Tunicate Worms. They are semi-transparent creatures of oval 

 or elongated form, and usually of a pale yellow, brown, or pink 

 colour ; and derive their popular name from the fact that they are 

 covered externally by a continuous tunic or wall of tough structure. 

 Although the tunicates resemble worms in many points of 



FIG. 124. Flustra 

 IN ITS CELL, 

 MAGNIFIED 



