Glochidium or veliger larva is a minute larva 0.1 to 0.4 mm wide of molluscs. Tremendrous number of glochidia are produced which fill the outer gill laminae. When sufficiently mature they are expelled through the exhalent siphon into the surrounding water. After some time they must come in contact with a fresh water fish as ectoparasites for about 10. Weeks during which they undergo a Peculiar metamorphosis to develops into young adults. The development of echinoderms include three larval stage i.e., dipleurula, bipinnaria and brachiolaria. The arthropods show both direct and indirect development, Nauplius metanauplius, Protozoa, Zoaea, Cypris mysis or schizopod Megalopa, Phyllosoma, Alima are common larvae.