ZOOLOG"£ AND BOTANY, MICROSCOPY, ETC. 287 



tests. During tlie boiling in acid, or burning on mica, tbe fluid 

 contents would burst tbe films, and in many cases leave behind tbe 

 evidence of their former condition. In bis experience, such evidence 

 has never been forthcoming, and, judging from what is known of 

 cellular structure in organic life generally, there are no examples of 

 truly vacuous cavities, inasmuch as all organic tissues are pervious to 

 dialytic or osmotic action. 



It is no doubt true that the organic silica of the diatom, perfectly 

 hyaline as it looks, is in reality a " colloid," and hence, as it contains 

 an infinitesimal percentage of water, just as flint itself does, dialytic 

 action may take place through the film under notice. But even then 

 the perviousness to moisture of the diatom, if it really keeps the 

 chamberlets full of fluid during the vitality of the organism, would 

 not suffice to settle the question ; for, if any fluid whatever remained 

 in the cellules, should the specimens have been but recently taken 

 from their element, it would burst the film on the application of heat, 

 and inevitably burst the walls, whilst traces of the disruption would 

 occasionally be visible under the Microscope. Again, if the 

 chamberlets contained gas of any kind, and in spite of the effects of 

 the boiling in acids, this gas were too minute in quantity to burst the 

 walls, we should certainly be able to detect gas bubbles in some of 

 the chamberlets. But, as is well known, the bubbles so common in 

 mounted specimens are not due to the cellules having originally con- 

 tained gaseous material, but to the accidental admission of air during 

 mounting. 



The only remaining alternative is that the cellules cannot be 

 considered closed cavities, and hence that the alleged presence of an 

 external investing and closing film is illusory. 



Lagerstedt's Diatom-sjmonymy.* — In view of the imperfect 

 figures and descriptions in Kiitzing's Fresh-water Alg^e of Germany, 

 N. G. W. Lagerstedt has worked out the dried specimens in the 

 museum at Stockholm, in order to determine more exactly the 

 synonymy of the species. Thirty-six species are treated in this 

 publication, and the following are figured : — Frustulia Ulna, Ach- 

 nanihes intermedia, Exilaria Vaucherice, Diatoma tenue, Frustulia 

 lanceolata, F. maculata, Fragilaria jpectinalis, and Brachysira aponina. 



Diatomaceous Deposits in Scotland. f — Prof. W. T. Macadam 

 records the discovery in Scotland of larger diatomaceous deposits 

 than any yet found. The deposit at Black Moss, Aberdeenshire, 

 contains over 800,000 cubic yards. Those of Ordie and Kinnord at 

 least an equal quantity. That at Gross, Lewis, occupies a basin- 

 shaped cavity, not many feet above sea-level, and said to be more 

 than 12 feet deep. The Glen Shira deposit is however likely to 

 prove the largest. The material is generally found forming a bottom 

 layer or stratum underlying peat. Analyses of the various deposits 

 are appended. 



* Ofvers. K. Svenska Vet. Akad. Forhandl., 1884, pp. 29-6i (1 pi ) See 

 Bot. Centralbl., xx. (1884) p. 93. 



t Mineral. Mag., vi. (1884; pp. 87-9. 



