| Answer | Crossword Clue |
|---|---|
| phototonuses | PHOTOTONUS, the sensitivity of a living organism to light |
| phototonic | relating to phototonus, the sensitivity of a living organism to light |
| phototonus | the sensitivity of a living organism to light |
| photoreceptor | A structure in a living organism, esp. a sensory cell or sense organ, that responds to light falling on it |
| photoreceptors | A structure in a living organism, esp. a sensory cell or sense organ, that responds to light falling on it |
