clade, most members of which alternate between polyp and medusa stages.

The hydrozoans display what can be thought of as classic or cnidarian life cycle, where polyp forms give rise to multiple medusa forms, with the latter the stage. The genus that includes is a prominent example of a hydrozoan, one that is typically featured when illustrating this alternating life cycle.

The , perhaps not surprisingly, are included among the hydrozoans. These are members of phylum Cnidaria that exist solely as polyps. The hydras, like hydrozoans generally, produce new asexually, except that these new individuals are polyps rather than medusas, with the polyps also serving as the stage when sexual reproduction is undertaken.

Note that hydrozoans do not display an alternation of generations since the polyp and medusa are members of the same generation, with the next generation formed via release of and along with subsequent zygote formation.