Eyestalk

Pulmonate land snails usually have two sets of tentacles on their head: the upper pair have an eye at the end; the lower pair are for olfaction.

An Eyestalk, eye stalk or ommatophore is a feature that moves an eye away from the body in anatomy. That way, the eye has a better field of view. Eyestalks are a specialized type of tentacle. Tentacles may also have olfactory organs at their ends. Examples of creatures with olfactory tentacles include snails, the trilobite superfamily Asaphida, and the fly family Diopsidae. In slugs and snails, these tentacles will regrow if severely damaged, and in some species, are retractable. Crustaceans also have eyestalks, consisting of two segments.

Gallery

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  A stalk-eyed fly.
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  Well-developed eye of Eustrombus gigas on eyestalk. There is also a small tentacle on the eyestalk.
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  Eyestalk of a lobster.