An hypothesis to account for a basic distinction between rods and cones.
D000818:Animals; D001001:Anura; D001345:Autoradiography; D000882:Haplorhini; D008251:Macaca; D051379:Mice; D008854:Microscopy, Electron; D010786:Photoreceptor Cells / Q000033:anatomy & histology* / Q000166:cytology / Q000254:growth & development; D051381:Rats; D014562:Caudata