What is one of the movable, slender, spinelike organs or parts with which certain bryozoans are furnished. They are regarded as specially modified zooids, of nearly the same nature as Avicularia called?

vibraculum — One of the movable, slender, spinelike organs or parts with which certain bryozoans are furnished. They are regarded as specially modified zooids, of nearly the same nature as Avicularia. (Webster's 1913.)