He had continued the same work by tracing homologies of development in other classes of animals, such as the Cephalous Mollusca, the Articulata, and the Brachiopods. On these subjects, also, he had a good deal of correspondence with other investigators of the same cast of mind, and even when he did not carry conviction, the impression made by his arguments may be judged from the words of Dr. Allman, no mean authority, in a letter of May 2, 1852:--] I have thought over your arguments again and again, and while I am the more convinced of their ingenuity, originality, and STRENGTH, I yet feel ashamed to confess that I too must exclaim "tenax propositi." When was it otherwise in controversy? [Other speculations arising out of these researches had been given to the public in the form of lectures, notably that on Animal Individuality at the Royal Institution in 1852. But after 1854, Paleontology and administrative work began to claim much of the time he would willingly have bestowed upon distinctly zoological research. His lectures on Natural History of course demanded a good deal of first-hand investigation, and not only occasional notes in his fragmentary journals, but a vast mass of drawings now preserved at South Kensington attest the amount of work he still managed to give to these subjects. But with the exception of the Hunterian Lectures of 1868, he only published one paper on Invertebrates as late as 1860; and only half a dozen, not counting the belated "Oceanic Hydrozoa," bear 1856 and 1859. The essay on the Crayfish did not appear until after he had left Jermyn Street and Paleontology for South Kensington. The "Method of Paleontology," published in 1856, was the first of a long series of papers dealing with fossil creatures, the description of which fell to him as Naturalist to the Geological Survey. By 1860 he had published twelve such papers, and by 1871 twenty-six more, or thirty-eight in sixteen years. It was a curious irony of fate that led him into this position. He writes in his Autobiography that, when Sir Henry de la Beche, the Director-General of the Geological Survey, offered him the post Forbes vacated of Paleontologist and Lecturer on Natural History,] I refused the former point blank, and accepted the latter only provisionally, telling Sir Henry that I did not care for fossils, and that I should give up Natural History as soon as I could get a physiological post. But I held the office for thirty-one years, and a large part of my work has been paleontological. [Yet the diversion was not without great use. A wide knowledge of paleontology offered a key to many problems that were hotly debated in the years of battle following the publication of the "Origin of Species" in 1859, as well as providing fresh subject-matter for the lectures in which he continued to give the lay world the results of his thought.