 Complete the following phrase:  The botanist Joseph Dalton Hooker, then aged 23 and the youngest person on the expedition, was assistant-surgeon to Robert McCormick, and responsible for collecting zoological and geological specimens. Thomas Abernethy, who had been on previous Arctic expeditions with Ross, was gunner. Hooker later became one of Englands greatest botanists; he was a close friend of Charles Darwin, and became director of the Royal Botanical Gardens, Kew for twenty years. McCormick had been ships surgeon for the 