MTL - 4.6 Billion Year Symphony of Evolution - Chapter 21 eyeball

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Lin has built a huge semi-circular shield into a 'cell wall' name, and the cell wall is composed of three layers of cells. The outermost layer is called 'cortex', which is the thickest and most flexible. One layer, inside

The two layers of the layer are called the middle and inner walls, and the thickness is not strong. However, if the cortex is damaged by some factors, the inner layer will harden quickly to prevent any threat from the outside from going further.