Source : Webster's Revised Unabridged Dictionary (1913)

Vorticella \Vor`ti*cel"la\, n.; pl. E. {Vorticellas}, L.
   {Vorticell[ae]}. [NL., dim. fr. L. vortex. See {Vortex}.]
   (Zo["o]l.)
   Any one of numerous species of ciliated Infusoria belonging
   to {Vorticella} and many other genera of the family
   {Vorticellid[ae]}. They have a more or less bell-shaped body
   with a circle of vibrating cilia around the oral disk. Most
   of the species have slender, contractile stems, either simple
   or branched.

Source : WordNet®

vorticella
     n : any of various protozoa having a transparent goblet-shaped
         body with a retractile stalk
     [also: {vorticellae} (pl)]

vorticellae
     See {vorticella}