(a) The colour of an object is under the control of the pigment visual violet that is Rodopsin that works in daylight and is sensitive to bright light and colours. There are three different types of pigments under the catogory of Rodopsin: (i) Erythrolable. It is most sensitive to red light. (ii) Chlordolable. It is most sensitive to green light. (iii) Cyanolable. It is sensitive to blue light. The combination of these three pigments produces all the colours that we can see. (b) Equilibrium. It is the controlled by statoreceptors present in the cristae ampullaes or semicircular ducts and the maculae of vestibule. Cristae control the dynamic equilibrium (when in motion) and equilibrium during angular head). As three semicircular ducts are in three different directions so these can detect the disturbances in position in different directions. Maculae control the static equilibrium (tilting of head or body at rest) and linear acceleration (rapid forward movements). (c) The amount of light entering the retina is under the control of two types of muscles present in the iris (sphincters) and radial muscles (dilators). The iris controls the amount of light falling over the retina by the radial muscles contracting in dim light and the circular muscles contracting in bright light.