Chap. 27 



AN AQUATIC MISCELLANY 



545 



Young Colony 



Sfotoblosis 



Units of Colony (x) 



Moture Colony 



Fig. 27.11. Bryozoan colonies. Upper, Marine. Encrusting colonies that live in 

 patches of their own limy deposits on rocks and seaweeds. The common Bugula 

 turrita that at first glance seems to be a delicate seaweed growing in tufts but 

 a few inches high. Lower, Fresh Water. Left, Plumatella spreads like a dark vine 

 over the stones in running water. Photograph of a living colony. The white 

 tips are the crowns of the zooecia with the tentacles withdrawn. Right, Pectinatella 

 magnifica, with its core of jelly, is a compound of many colonies. Floating in a 

 pond it appears to be a great green pineapple, each of its colonies taking the 

 place of the units of fruit. {Upper, courtesy, American Museum of Natural 

 History, New York. Lower right, courtesy. Ward and Whipple: Fresh Water 

 Biology. New York, John Wiley and Sons, 1918.) 



Bugula and bryozoans of a similar type have a true coelom lined with a 

 cellular peritoneum. The coelomic fluid contains corpuscles and is the main 

 carrier of substances to and from the cells. There are no special organs of 

 respiration, excretion, or circulation. In the smaller class Endoprocta, gelat- 

 inous mesenchyme fills the space occupied by the coelom in the ectoprocts 

 such as Bugula. The ganglion or "brain" is connected by nerves with the ten- 

 tacles and retractile muscles. 



Many bryozoans have minute pincers scattered over their outer surfaces, 

 believed to be very specialized individual animals rather than appendages. 



