A Cat's Pupil

Figure 1. A Cat's Pupil. Depending on the relative light present, the shape of a domestic cat's pupil changes from a vertical slit, to an almond shape, to almost fully round. Photo by wapiko available at: https://farm8.staticflickr.com/7170/6485554303_293163fb27_o_d.jpg under CC BY 2.0 license.