MAY be very differently modified in ADAPTATION to different functions. For example ? in case of whales hind limbs are only represented INTERNALLY and are not apparent externally, the forelimbs modified into paddles and retain the bones of the shoulder, forearm, wrist and fingers all of which are enclosed in a fin-shaped sac; the head is fish-like but POSSESSES all the mammalian bones. Analogous organs are structurally different organs which get modified to perform SIMILAR functions.