ABSTRACT.    The molecular study shows now that Myxozoa are closer to Cnidaria. The two groups are present exclusively in aquatic environment and use water like vector for proliferation and dissemination. During their life cycle, Cnidaria pass from a sessile phase fixed on substrates (the Polype form), to a planktonic free phase (planula and jellyfish). Myxozoa have also a planctonic and non planctonic phase. The planctonic form results from the sexual reproduction into an annelid. This is actinospore. The non planctonic form the asexual multiplication that tack place in fishes. However the knowledge on the sexuality of Cnidarians shows that it is very distant from Myxozoa, still almost unknown. This is because the absence of centrioles, wich means that there are no lashes and no flagella in Myxozoa. Myxozoa produce isomorphous gametes alpha and beta in a closed space, called pansporocyste. The existence of the planktonic forms ensures the meeting Actinospore fish. The death of parasitized fish generally creates at the bottom of water a microbiotope allowing the contact Myxospores- Annelid.