Page:Journal of botany, British and foreign, Volume 34 (1896).djvu/344

 318 THE REPRODUCTION OF DIATOMS. permission to reproduce the accompanying portrait, which is from a photograph of an original painting in the possession of Mrs. Grover, the widow of one of Ehret's lineal descendants. THE REPRODUCTION OF DIATOMS. At the meeting of the Linnean Society on June 18th, Mr. George Murray, who had made a study of living pelagic Diatoms while on a cruise round the coasts of Scotland in March and April, on behalf of the Fishery Board for Scotland, exhibited a series of lantern slides, illustrating new forms of reproduction in Diatoms. He attributed the novehy of his observations, not only to the initiative of the Fishery Board, and especially of Dr. John Murray, but to the fact that he was almost the first botanist who had gone down to the sea in a ship armed with suitable apparatus for such observations. The first slide was a reproduction of a figure by Prof. Cleve (" Diatoms of the Arctic Sea," in Bihang till K. Svensk. Akad. Haiidl.f Bd. I. No. 13, pi. I. fig. 3, a and b) of Biddulphia aurita in what might be called an encysted state, showing a young Biddulphia within the mother-cell. A similar state of things was known in other Diatoms, e. g. Biddulj^hia lavis and Navicula scotica, as Mr. Comber informed him, where new valves are formed within old ones in nests of two or three. The second slide was of Biddidphia mobiliensis, and not only showed a young Biddulphia without spines or external markings within an old one, but a still earlier stage exhibiting the contraction and rounding off of the cell-contents of the mother-cell. On the same slide a similar rounding off was seen in the cell-contents of Ditylum Brightwellii. Slide III. showed a valve of Coscinodiscus concinnus with a new Diatom within it and, what carried matters a stage further, a valve with a pair of new Diatoms. Slide IV. showed the same species with cell-contents divided into eight and into sixteen rounded-off portions; and Slide V. free packets of eight and of sixteen young Diatoms held together by a fine membrane, as they had doubtless escaped from a parent-cell. Mr. Murray had observed numerous states which might or might not be intermediate between the two last states, but there was not sufficient certainty to justify him putting them on record. He believed that in this free packet stage the walls, though finely sculptured, were not or were imperfectly silicified, and capable of expansion and growth. His reason for this belief was grounded on the observation that all such early stages disappeared on "cleaning" with nitric acid, but he pointed out that there could be no certainty on this point unless after direct observation of individual cases, a matter involving difficulties of manipulation he had not yet overcome. In Slide VI. there were shown two diagrammatic figures of the same filament of Chatoceras decipiens, as observed in successive stages of contraction of the cell-contents, their rounding off, and the pro- duction by free-cell-formation of eight spore-like bodies. In the case of Biddulphia and Ditylum, and in the first case of Coscinodiscus, where one new Diatom was produced, it appeared to