Apple snails possess structurally complex eyes at the tip of a cephalic eyestalk. Excising the eyestalk in young crayfish produces glucagon-induced hyperglycemia. Each eyestalk has a small sensory tentacle branching off near the end. The exact mechanism of eyestalk ablation on the ovarian maturation is not conclusive. The animal's left eyestalk protrudes through this notch. The Doctor throws his hat on the Dalek's eyestalk, blinding it, then destroying it. A small depression serves for eye muscle attachment ventral to the eyestalk area. This corresponds to the eyestalk attachment reported in basal bony fishes. In invertebrate animals, eyestalk removal has been reported to affect glucagon production. The eyestalk was designed to be level with Smith's eyeline. Bellybomb is an alien outlaw with one eyestalk and a mouth on his stomach. The space between the eyes is much shorter than the eyestalk. Eyestalk length increases with body size, and males with shorter eyestalks will usually retreat. Eyestalk ablation is the removal of one or both eyestalks from a crustacean. Its eyestalk has been replaced with a conventional torch, which flashes when it speaks.