The Oceanic Hydrozoa is a seminal piece of marked distinction by Huxley, the eminent biologist, nicknamed Darwin's bulldog for his advocacy of Charles Darwin's theory of evolution. This monograph, first published by the Ray Society in 1859, is a description of the Calycophoridae and Physophoridae observed whilst Huxley served as Assistant-Surgeon on the survey vessel HMS Rattlesnake in the years 1846-50. The twelve plates at the back of the book have become an invaluable record of the study of the Oceanic Hydrozoa.