The first direct proof of the existence of an invertebrate fauna in deep seas was found by the expedition that was sent to repair the submarine cable of the Mediterranean Telegraph Company. The cable had broken in deep water, and a ship was sent out to examine and repair the damage. When the broken cable was brought on deck, it bore several forms of animal life that must have become attached to it and lived at the bottom of the sea in water extending down to a depth of 1,200 fathoms. Among other forms a _Caryophyllia_ was found attached to the cable at 1,100 fathoms, an oyster (_Ostrea cochlear_), two species of Pecten, two gasteropods, and several worms. The discoveries that had been made indicating the existence of a deep-sea fauna led to the commission of H.M. ships ‘Lightning’ and ‘Porcupine,’ and the systematic investigation that was made by the naturalists on these vessels brought home to the minds of naturalists the fact that there is not only an abysmal fauna, but that in places this deep-sea fauna is very rich and extensive. The ‘Lightning’ was despatched in the spring of 1868 and carried on its investigations in the neighbourhood of the Faeroe Islands, but the vessel was not suitable for the purpose and met with bad weather. The results, however, were of extreme importance; for, besides solving many important points concerning the distribution of ocean temperature, ‘it had been shown beyond question that animal life is both varied and abundant at depths in the ocean down to 650 fathoms at least, notwithstanding the extraordinary conditions to which animals are there exposed.’ Among the remarkable animals dredged by the ‘Lightning’ were the curious Echinoderm, _Brisinga coronata_, previously discovered by Sars, and the Hexactinellid sponges, _Holtenia_ and _Hyalonema_, the Crinoids _Rhizocrinus_ and _Antedon celticus_, and the Pennatulid _Bathyptilum Carpenteri_, not to mention numerous Foraminifera new to science. In the spring of the following year, 1869, the Lords Commissioners of the Admiralty despatched the surveying vessel ‘Porcupine’ to carry on the work commenced by the ‘Lightning.’ The first cruise was on the west coast of Ireland, the second cruise to the Bay of Biscay, where dredging was satisfactorily carried on to a depth of 2,435 fathoms, and the third in the Channel between Faeroe and Scotland. The dredging in 2,435 fathoms was quite successful, and the dredge contained several Mollusca, including new species of _Dentalium_, _Pecten_, _Dacrydium_, &c., numerous Crustacea and a few Annelids and Gephyrea, besides Echinoderma and Protozoa. A satisfactory dredging was also made in 1,207 fathoms. The third cruise was also successful and brought many new species to light, including the _Porocidaris purpurata_, and a remarkable heart urchin, _Pourtalesia Jeffreysi_. Concerning Pourtalesia Sir Wyville Thomson says:—