epizoon

Epizoon, ep-i-zō′on, n. a parasitic animal that lives on the bodies of other animals and derives its nourishment from the skin—also Epizō′an:—pl.

Upon some very remarkable new forms of Annelids, and especially upon the much contested genus Sagitta, which I have evidence to show is neither a Mollusc nor an Epizoon, but an Annelid.