What Scientists Call Evolution is Only Adaptation
     Moles have subcutaneous eyes. cave fish have no eyes, but their skulls clearly indicate that their ancestors did.  Whales have vestigial hipbones. Organs and limbs don't disappear due to adaptation.  they disappear because of evolution.  The creature no longer has the need to divert energies toward building these organs and limbs, so the information for building them gets edited out of their genetic codes.