INVERTEBRATE ZOOLOGY IN THREE BOOKS - BOOK 1 - H.Y. Shcherbak - 1995

SUBKINGDOM MULTICELLULAR ANIMALS (METAZOA)

SECTION TRUE METAZOANS (EUMETAZOA)

PHYLUM CNIDARIA (OR COELENTERATA)

CLASS HYDROZOA

These are mostly small solitary and colonial organisms that exhibit either a polyp or a medusa form. Coloniality is widespread among polyps. Colonies can be monomorphic, consisting of identical polyps, or polymorphic, featuring Different types of polyps. The gastrovascular cavity of polyps is sac-like and lacks septa; Gonads develop in the ectoderm. The Class encompasses approximately 4,000 predominantly marine species, with only a few dozen inhabiting freshwater environments.

The Class Hydrozoa is divided into two subclasses: Hydroidea and Siphonophora.



Last update: 13/08/2026

Editorial and Educational Adaptation: This material has been compiled based on the primary/original source text. The project team performed an editorial review, corrected technical inaccuracies, structured sections, and adapted the content for an educational format.

What was processed:

  • elimination of formatting defects (OCR errors, structural breaks, corrupted characters);
  • editorial organization of content;
  • standardization of terminology in accordance with academic sources;
  • verification of factual statements against the original source text.

All mentions of the author, publication year, and origin of the primary text have been preserved in accordance with the source.