Mr. Marshall Hall’s yacht, the ‘Norma,’ was employed for some time in this work, and an extensive collection of deep-sea animals was made. About the same time Professor L. Agassiz was busy on board the American ship, the ‘Hassler,’ in continuing the work of Count Pourtales, and later on the Germans fitted out the ‘Gazelle,’ and the French the still more famous ‘Travailleur’ and ‘Talisman’ expeditions. Nor must we omit to mention in this connection the cruise of the Italian vessel, the ‘Vittor Pessani,’ nor those of the British surveying vessels, the ‘Knight Errant’ and the ‘Triton,’ and the American vessels, ‘The Blake’ and the ‘Fish Hawk.’ But of all these expeditions, by far the most complete in all the details of equipment, and the arrangements made for the publication of the results, was the expedition fitted out in 1873 by the British Government. The voyage of H.M.S. ‘Challenger’ is so familiar to all who take an interest in the progress of scientific discovery, that it is not necessary to do more than make a passing mention of it in this place. The excellent books that were written by Wyville Thomson, by Moseley, and by other members of the staff, have made the general reader familiar with the narrative of that remarkable cruise and the most striking of the many scientific discoveries that were made; while the numerous large monographs that have been published during the past fourteen years give opportunities to the naturalist of obtaining all the requisite information concerning the detailed results of the expedition. The expenditure of the large sum of money upon this expedition and the publication of its reports has been abundantly justified. The information obtained by the ‘Challenger’ will be for many years to come the nucleus of our knowledge of the deep-sea fauna, the centre around which all new facts will cluster, and the guide for further investigations. To say that the ‘Challenger’ accomplished all that was expected or required would be to over-estimate the value of this great expedition, but nevertheless it is difficult for us, even now, thoroughly to grasp the importance of the results obtained or to analyse and classify the numerous and very remarkable facts that were gained during her four years’ cruise.