[nudephil (OP)]

Here's a question sent in by George:

What is the reason behind the difference in shape between rod and cone photoreceptor cells?

Can anyone answer?

[Petrochemicals]

Ill have a go,

The rods and the cones are about detail versus movement,  rods heavily dependant on red light and its heavy handed nature do differentiate movement, not that detailed but efficient at protection and hunting, just like the t rex in jurassic park. The cones are there to give the technicolour vision in detail for desision making.