Flatworms

Taxonomic Classification

Kingdom:	Animalia
Subkingdom:	Eumetazoa
Clade:	ParaHoxozoa
Clade:	Bilateria
Clade:	Nephrozoa
Unranked:	Protostomia
Unranked:	Spiralia
Clade:	Rouphozoa
Phylum:	Platyhelminthes
Source: Integrated Taxonomic Information System

Attribute	Cnidarians and Ctenophores	Platyhelminthes (flatworms)
Bilateral symmetry	No	Yes
Number of main cell layers	Two, with jelly-like layer between them (mesoglea)	Three
Distinct brain	No	Yes
Specialized digestive system	No	Yes
Specialized excretory system	No	Yes
Body cavity containing internal organs	No		Yes
Specialized circulatory and respiratory organs	No		Yes
Cnidocytes	Yes	No
Colloblasts	No	Yes	No		Bilateral symmetry	No		Yes
Number of main cell layers	Two, with jelly-like layer between them		Three
Distinct brain	No		Yes
Specialized digestive system	No		Yes
Specialized excretory system	No		Yes
Body cavity containing internal organs	No			Yes
Specialized circulatory and respiratory organs	No			Yes

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