Parasitic upon Polyzoa, etc. circinate branched--branches irregular divaricate.
Polyzoa means "many animals," in allusion to their habit of living in association.
Yet the echinus can have, at the best, none but the most distant genetic relationship with the Polyzoa.
There are two divisions of the Polyzoa, the Ectoprocta and the Endoprocta.
The stomach is a bulky organ that differs markedly in form and structure in different groups of polyzoa.
