conomyoidin

Contractile protoplasm at the inner end of the inner segment of retinal cones; motility is most evident in fishes and amphibians, and slight or absent in mammals. [G. konos, cone, + mys, muscle, + eidos, resemblance]

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co·no·my·oi·din (ko″no-mi-oiґdin) [cono- + myoid] a protoplasmic material within some retinal cones that expands and contracts under the influence of light, causing the cones to shift position.