What role did Thomas Henry Huxley have aboard HMS Rattlesnake?

Thomas Henry Huxley served as an assistant surgeon aboard HMS Rattlesnake from 1846 to 1850 during its survey of the Great Barrier Reef and New Guinea.1

While his primary role was medical, he utilized the voyage to conduct significant scientific research. Working with a microscope in the ship's chart room, he performed pathbreaking studies on marine invertebrates, including sea anemones, jellyfish, and the Portuguese man-of-war. His observations led him to classify these organisms as Nematophora—later identified as the phylum Cnidaria—and to propose that they were composed of two "foundation membranes," which he linked to the embryonic cell layers of vertebrates. Additionally, his notes on the larval sea squirt provided evidence that would later help establish the evolutionary link between ascidians and vertebrates.1