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recent Foraminifera of Great Britain, after publishing a number of
shorter memoirs on the group.
In 1851-2 Williamson made a careful study of the organisation of Volvox Globator, and brought out facts as to the mode of connection between its cells, which have only been verified by other observers within the last few years. This was probably his best contribution to recent botany.
Shortly before this date Williamson had undertaken an investigation of a totally different kind, namely, the development of the teeth and bones of fishes, which he considered in relation to the cell theory. His results in this field were of great importance, and are embodied in two papers published in the Philosophical Transactions of the Royal Society' for 1849 and 1851. The value of these investigations was recognised by his election as a Fellow of the Royal Society in 1854.
Previously to this, in January, 1851, Williamson had entered the ranks of official teachers of Science, by his appointment as Professor of Natural History in the newly founded Owens College at Manchester This was an arduous post, for the subjects to be taught included three sciences zoology, botany, and geology. At first he found it possible to deal with this formidable task, by spreading his complete coursc over two years, a wise arrangement under the circumstances, but one which the exigencies of the examination system ultimately rendered impracticable. This led in 1872 to a division of the duties of the chair, Williamson being then relieved of the geological part of the teaching by Professor Boyd Dawkins. The remaining work, however, was still far too extensive for any one teacher, and in 1880 a further division of labour took place. The late Professor Milnes Marshall occupied the chair of zoology, while Williamson retained that of botany, which he continued to hold till 1892.
In addition to his strictly official work as Professor, Williamson was one of the first two members of the staff, who, as early as 1854, started evening classes for working men. In later years, he met with extraordinary success as a popular scientific lecturer, more especially for the Gilchrist Trustees, for whom he delivered some hundreds of lectures during the period from 1874 to 1890. His power of rousing and retaining the interest of great popular audiences is described by those who have heard him as most remarkable.
During a great part of the time at Owens College, Williamson continued in active and successful practice as a physician. In the midst of all his multifarions duties, as professor, popular lecturer, and medical practitioner, he always found time for original scientific work; rarely has so busy a man done so much for the advancement of science by actual research.
So far, little has been said of the work of Williamson on fossil
