Which marine animals did Thomas Henry Huxley study during the Rattlesnake voyage?

During his service as an assistant surgeon on the HMS Rattlesnake between 1846 and 1850, Thomas Henry Huxley conducted significant research on various marine animals. Using a microscope in the ship's chart room, he studied the structure and growth of the following organisms:

• Sea anemones1
• Hydras1
• Jellyfish1
• Sea nettles, including the Portuguese man-of-war1
• Sea squirts (ascidians)1

Huxley grouped the sea anemones, hydras, jellyfish, and sea nettles together as Nematophora, which were later classified as the phylum Cnidaria. His observations of these creatures led him to identify two "foundation membranes"—now known as ectoderm and endoderm—and he famously noted that the larval sea squirt possesses tail muscles similar to those of a tadpole, a discovery that later contributed to the understanding of their evolutionary relationship to vertebrates.1