Losing Limbs and Organs is Devolution, Not Evolution
     Oh, so you can have one and not the other?  Eyes are soft tissue and easily damaged.  If they are no longer needed, it makes perfect sense to evolve away from them, as they are now a hinderance, a waste of energy to build and maintain, and an area of vulnerability to attack.  In water, legs would increase resistance, slowing the creature, and again present targets of attack for predators, so water dwelling animals evolved away from legs..  These are indications of evolution, not devolution, whatever that is.