In almost all vertebrates when the optic cup fails to develop in the embryo the lens also fails to form the constitutes evidence that

The optic cup is responsible for the formation of lens.

Explanation:

The process of formation of vertebrate optic cup begins when optic vesicle comes in contact with ectoderm. The developing brain side bulge give rise to optic cup. The surface ectoderm is responsible for lens formation. Thus, when the optic cup fails to develop in the embryo the lens also fails to form in the development of embryo.

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