The expedition consisted of two ships, HMS "Erebus" and HMS "Terror"; it was the last major voyage of exploration made entirely under sail. Hooker was the youngest of the 128 man crew. He sailed on the "Erebus" and was assistant to the ship's surgeon, who was instructed to collect zoological and geological specimens. The ships travelled all over the southern oceans from South America to Australia and New Zealand. Hooker made plant collections at each location and while travelling drew these and specimens of algae and sea life pulled aboard using tow nets.