Outlines the characteristics of this group of polyps and medusae.

Complete the membership application, and peruse links to Web sites about this group of polyps and medusae.

Profiles the fossil record, life cycle, physical structure of hydrozoans such as the Portuguese Man-of-War.

Peruse a description of this aquatic creature's appearance, propulsion systems, and feeding habits. Link to related resources.

Find a profile of this invertebrate class, including details on various species and reproductive cycles. Includes related links.

Get facts about the tentacles, life cycle and structure of this dangerous animal.