and some speculations on the development of certain medusoid forms, which attracted notice and were considered too daring by Johnston and Edward Forbes. During this period, too, he entered upon those researches of the crinoids of past times and the crinoidal forms of modern times, of which he took Comatula rosacea as a typical specimen, which, with their direct and indirect results, led him up to the grand work of his life. A British pentacrinus had been discovered and described by Vaughn Thompson thirty years before, and determined by him to be but the young stage of the "rosy feather-star," but nothing more bad been learned about it. Professor Thomson undertook to complete the investigation and fill out the life-history of the animal; and the account of his researches was given to the Royal Society in 1862 and published in the volume of the "Philosophical Transactions" for 1865. This investigation on the pentacrinoid stages of comatula was but a part of a series of observations on the genus Pentacrinus itself, and Professor Thomson collected a mass of material with the object of writing a memoir on the group.
Up to nearly this time, it had not been believed by scientific men that life did or could exist below a certain depth of the sea. Professor Forbes had admitted the existence of a zone of deep-sea coral extending from fifty fathoms below the surface to an unknown depth, a region in which, he held, "as we descend deeper and deeper, its inhabitants become more and more modified and fewer and fewer, indicating our approach toward an abyss where life is either extinguished or exhibits but a few sparks to mark its lingering presence." This skepticism, however, was becoming weaker under the testimony of living specimens that were from time to time brought up from undoubtedly great depths.
About 1864, Mr. G. O. Sars, of the Norway Fisheries Commission, dredged up a number of specimens of a strange crinoid from a depth of seven hundred feet, and, continuing to dredge, found an abundance of animal life at about the same depth. Professor Thomson was invited by Sars's father, the illustrious Professor Michael Sars, to visit Christiania and see the specimens. The two, after examining them, concluded that they were closely related to one of the fossil genera, allied to the family of the Apiocrinidæ. Here, then, they had a living representative of a group supposed to be extinct, and of a form which had lived over from the Cretaceous epoch.
In 1868 Dr. Carpenter, being engaged in investigations on a living crinoid from the West Indies, visited Professor Thomson to discuss the subject in which they were both interested; and on this occasion Thomson told his visitor that the one unexplored field awaiting the investigation of naturalists was the sea; that he was convinced that when explored it would yield immense treasures to science; and suggested to him to use his influence with the Admiralty to secure the grant of a vessel, suitably fitted up for deep-sea research. The use of