Assertion: gray squirrel | /r/HasAspect | two-tiered retina
Facets:
Source sentences:
text: Grey squirrels (and probably Reds) have a two-tiered retina: one tier in the centre of the retina is composed of rod cells that are used in low light and provide monochrome vision, and the outer tier is composed of colour-sensitive cone cells – the rod to cone ratio in Greys is about 2:3.