126 BEYOZOA. 



shore, the cells (fig. 26 a) having slit-like valvular 

 orifices. The bodies of the animals are soft and 

 polype-like, and are furnished at one end with a circle 

 of tentacles, covered with rows of cilia, by which the 

 water is changed for respiration, and particles of food 

 are brought to the mouth. The tentacles can be 

 protruded or withdrawn at the will of the animal. 

 The Bryozoa are what are called compound animals, 

 each individual body having its own set of organs ; 

 yet the whole are connected together. 



The two species figured are very common. Fludtra 

 folidcea (PL IX. fig. 27) is found everywhere upon 

 the sea-shore. The polypidom has cells upon both 

 sides ; and they are narrowed at one end, and rounded 

 at the other. Membranip'ora pilosa (PL IX. fig. 39) 

 occurs upon sea- weeds and other marine bodies, form- 

 ing a closely adherent layer. The orifices of the cells 

 are surrounded with teeth, and are usually furnished 

 below with a very long bristle the polypidom appear- 

 ing to the naked eye as a white hairy crust. In the 

 variety figured, the long bristles are replaced by a 

 spine ; and this is not uncommon. 



The polypidoms of the Bryozoa form interesting 

 microscopic objects, the cells being furnished with 

 variously arranged spines and punctures or dots. In 

 some the cells are erect and arranged in rows upon the 

 branches of a plant-like stem, while in others they are 

 scattered irregularly over a creeping filament. 



For examination they should be prepared by macer- 

 ation in fresh water, and drying between glass plates 

 or sheets of paper, and either viewed as opake objects 

 or, after soaking in 'turpentine and mounting in bal- 

 sam, as transparent objects. 



It may be remarked that the name Bryozoa for 

 this class of Mollusca, which was thoroughly estab- 

 lished, has recently been changed in this country to 

 Polyzoa (TToXu?, many, o>ov, animal), and that the 

 name of polypidom has been altered to polyzoary. 



