Images below courtesy of Hydroids of Race Rocks



A hydrozoan polyp



A hydrozoan feeding polyp
Hydra image courtesy of UCMP Berkeley

Hydrozoas are distinguished by the fact that they are nearly always found in the polyp morph, although the medusa morph is possible in some stages of the lifecycle. When the medusa morph is found in a hydrozoa, it is much smaller than that of a schphozoa. Hydrozoas can be found in very diverse ecosystems, and appear very different, from a hydra to the Portugese man-of-war.

Information provided by: http://www.sidwell.edu