from The Century Dictionary.
- noun The only genus of fresh-water sponges, belonging to the group Fibrospongiæ.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Zoöl.) A genus of siliceous sponges found in fresh water.
Sorry, no etymologies found.
Both chemical and histological observations showed the abundant presence of starch in the green cells, and thus these planarians, and presumably also _Hydra spongilla_, etc., were proved to be truly "vegetating animals."