all marine invertebrate groups are present at this depth, and that deep-sea temperatures are not as constant as had been supposed, but vary considerably, and indicate oceanic circulation. These results were described in The Depths of the Sea, which he published in 1873. Challenger expedition The remarkable hydrographic and zoological results which Wyville Thomson had demonstrated, in addition to the growing demands of ocean telegraphy, soon led to the Royal Navy to grant use of for a global expedition. Wyville Thomson was selected as chief scientist, and the ship sailed on 23 December 1872. Aftermath The Challenger Expedition was deemed a great success, and on his return Wyville Thomson received a number of academic honours, as well as a knighthood. In 1880 he published in two volumes (having completed writing in 1877), The Voyage of the Challenger in the Atlantic, a preliminary account of the results of the voyage. He spent the next two years working on administrative duties connected with the publication of the full monograph of the voyage. Wyville Thomson had a highly strung mentality, and his health was generally poor throughout his life. He found dealing with publishers over the requirements of publishing 50 volumes of detailed illustration and scientific description enormously stressful. In 1879 he ceased to perform his university duties, gave up overseeing the reports of the expedition in 1881, took to his bed and died a broken man at Bonsyde on 10 March 1882. The publishing was finally completed by his friend and colleague Sir John Murray. Wyville Thomson is commemorated in the stained glass window above the altar in St. Michael's Parish Church, Linlithgow and his headstone is in the churchyard. In addition the Wyville-Thomson Ridge in the North Atlantic Ocean is named after him. Evolution Thomson had criticised natural selection, stating it was not enough to explain the evolution of species. Replying in the Nature journal, Charles Darwin commented that "I am sorry to find that Sir Wyville Thomson does not under stand the principle of natural selection, as explained by Mr. Wallace and myself... Can Sir Wyville Thomson name any one who has said that the evolution of species depends only on natural selection?" Publications The Depths of the Sea (1873) The Voyage of the Challenger (1877) Family In 1853 he married Jane Ramage Dawson. They were parents to Frank Wyville Thomson FRSE (1860–1918). Taxon named in his honor The Pallid