CHAPTER THIRTY 



BRYOZOA 



Characters i. THE Bryozoa (the term meaning " moss animals ") 



ofBryozoa n 



are small aquatic creatures, mostly marine, nearly 



From "Animate Creation" 



FIG. 54. Bryozoans, Plumatella, from fresh water. The upper figure greatly 



enlarged. 



always living in colonies or zoaria, often looking very 

 much like seaweeds or corals. Each separate individ- 

 ual (zooid) is placed in a membranous or calcareous 

 (limy) sac, called the zooecium. They differ entirely 

 from coral animals in possessing an alimentary canal 

 with two openings, and a well-developed nervous system, 

 distinct body cavity, etc. The mouth is surrounded by 

 delicate respiratory tentacles. The colonies are formed 

 by gemmation or budding, but the animals have sexual 

 organs, being usually hermaphroditic. There is no 

 heart or true blood system. 



The Bryozoa are of great antiquity, and are abun- 



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