The Handbuch der Zoologie/Handbook of Zoology was founded by Willi Kükenthal in Berlin, and treated the complete animal kingdom from single cell organisms to mammals in eight thematic volumes: Volume I: Protozoa, Porifera, Colenteratea, Mesozoa (1925); Volume 2: Worms (1933/34); Volume 3: Arthropoda ex. Insecta (1927/1932); Volume 4: Arthopoda: Insecta; Volume 5: Solenogastres, Mollusca, Echinoderma (1925); Volume 6: Pisces / Amphibia (1930); Volume 7: Reptilia / Aves (1931); Volume VIII Mammalia. As knowledge in these subjects increased, all volumes were later broken into several parts, and the set eventually included about 100 printed volumes, with the final volumes appearing in 2005.
In April 2017 a complete list of printed volumes published, including authors, titles, dates, and pagination, was available from degruyter.com at this link. The publishers also announced that:
"Beginning in 2010 the Handbook of Zoology will be restructured and offered additionally as a database (Zoology Online) which can be easily searched and rapidly updated. The eight thematic volumes will be replaced with smaller and more flexible groupings that reflect the current state of phylogenetic knowledge. Faster publication times through online-prepublication, reference linking, forward linking and multimedia presentations will make the Handbook of Zoology highly attractive to both authors and users."
Handbook of Zoology Online was available from degruyter.com at this link.