POLTZOA. 513 



upon its cell. The oral extremity is surrounded by a circle 

 oflong tubular tentacles covered with cilia ; at each of these 

 feelers or arms there is an aperture, the one at the base 

 communicating with a canal that passes round the edge of 

 the oral aperture or mouth. The food passes down a long 

 gullet, that contracts during the process of swallowing. At 

 the end of this is an orifice that opens into what appears 

 to be a gizzard, having two bodies opposite to each other, 

 with a rough surface, as if for the comminution of food, 

 moved by muscular fibres. Those of the species without 

 this gizzard have a digestive stomach that secretes a 

 coloured fluid. From the upper part of the stomach near 

 the entrance from the gizzard arises an intestine, having 

 a narrow opening surrounded by cilia that proceeds 

 upwards, ending in an orifice near to the tentacles, from 

 which the refuse food is ejected. 



Their cells are of various shapes, and from one, a family 

 of millions come, budding forth from its sides ; and 

 though the living matter disappears, the catacombs exist 

 for the foundation of their families, branching out and 

 enduring for ages. 



Bryozoon Boiverbankia received its name from Dr. Arthur 

 Farre, in honour of the well-known microscopist, Mr. 

 Bowerbank. A magnified representation of the animal is 

 seen in fig. 243. " When fully expanded, it is about one- 

 twelfth of an inch in length. In its retracted state, it is 

 completely enclosed in a delicate horny cell, sufficiently 

 transparent to admit of the whole structure of the con- 

 tained animal being seen through its walls. The cells are 

 connected together by a cylindrical creeping stem, upon 

 which they are thickly set, sessile, ascending from its 

 sides and upper surface. The animal, when completely 

 expanded, is seen to possess ten arms of about one-third 

 the length of the whole body ; each arm being thickly 

 ciliated on either side, and armed at the back by about 

 a dozen fine hair-like processes, which project at nearly 

 right angles from the tentacles, remaining motionless, 

 while the cilia are in constant and active vibration." 



Notamia, Bach-cell, so named from the cells being exactly 

 opposite, and united back to back with a thick partition, 

 and having a joint above and below each pair. In some 



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