n. [capitalized] In zoology, a generic name given to the young of certain fresh-water mussels, as Unio and Anodonta, which are hatched in the gills of the parent, and were at one time supposed to be parasites. Rathken. In botany, a hair-like appendage to the massulæ of heterosporous Filicineæ, by which the massulæ attach themselves to the macrospores after both have been discharged into the water.