Assertion: sand dollar's tube foot | /r/HasProperty | primary sites of gas exchange
Facets:
Source sentences:
text: Tube feet can also act as respiratory organs, and are the primary sites of gas exchange in heart urchins and sand dollars, both of which lack gills.
text: Tube feet can also act as respiratory organs, and are the primary sites of gas exchange in heart urchins and sand dollars, both of which lack gills.