Circulatory and Excretory Systems
The coelenteron functions as the internal transport system. Circulation of fluid in it is carried out by the ciliated gastrodermis, muscular contraction, or both1.
Excreted waste such as ammonia either diffuses across the body wall or readily dissolves into fluid circulated by ciliary action over the gastrodermis and epidermis1.
1Ruppert, Fox & Barnes 2004
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