318 THE KEPRODUCTION OF DIATOMS. 



permission to reproduce the accompanying portrait, wliicli is from 

 a photograph of an original painting in tlie 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 hehalf of the Fishery Board for Scotland, exhihited a series of 

 lantern slides, illustrating new forms of reproduction in Diatoms. 

 He attributed the novelty 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 Biluauj till K. Svmsk. Akad. 

 Haiidl., Bd. I. No. 13, pi, I. fig. 3, a and b) oi 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. Blddidphia Icevis and Nuvicula 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 Biddulphia 

 mobilioisis, 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 oil' was seen 

 in the cell-contents of Diti/lum Brit/lUwdlii. Slide III. showed a valve 

 of Coscinndiscus concinniis 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 difiiculties of manipulation he had not yet overcome. 

 In Slide VI. there were shown two diagrammatic figures of the same 

 filament of Chcctoceras dccipiens, as observed in successive stages of 

 contraction of the cell-contents, their rounding ofi', and the pro- 

 duction by free-cell-formation of eight spore-like bodies. 



In the case of Biddidphia and IHUjlum, and in the first case of 

 Coscinodiscvs, where one new Diatom was produced, it appeared to 



