ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 109 



genera also they are not invariably present, and always in Pleuro- 

 tcenium, Penium, and Tetmemorus, but were absent from all the 

 specimens examined of Staurastrum, Desmidium, and HyalotJieca. They 

 appear to be entirely confined to the Desmidiese, other fresh-water 

 algsB containing calcium oxalate, especially species of Spirogyra, but 

 not calcium sulphate. 



The absence of crystals of calcium sulphate, either occasionally 

 or regularly, does not, in the opinion of the author, imply the absence 

 of the salt ; since, from its solubility in water, it may be present in 

 the cell-sap. The zygospores of Closterium were always found to 

 contain crystals. Calcium sulphate is an excretory product in the 

 process of metastasis, corresponding to the production of calcium 

 oxalate in the higher plants ; and the quantity excreted determines 

 whether it shall remain entirely dissolved in the cell-sap, or whether 

 a portion of it shall separate in the form of crystals. 



MICEOSCOPY. 



a. Instrum.ents, Accessories, &c. 



"Giant Electric Microscope." — One of the attractions at the 

 Crystal Palace is what is advertised as " Les Invisibles in the Giant 

 Electric Microscope." We take the following description from a daily 

 paper,* no other description being forthcoming. " A number of gentle- 

 men assembled at the exhibition court of the Crystal Palace on 

 Saturday, by invitation of the directors, to witness the first repre- 

 sentation in England of ' Les Invisibles,' an exhibition of natural 

 objects magnified and displayed by means of the great electric 

 Microscope. The apparatus used in the exhibition is the invention of 

 Messrs. Bauer and Co., and ' Les Invisibles ' has quite recently 

 attracted a good many visitors to the old Comedie Parisienne, where, 

 as well as at the Athenseum at Nice, a series of representations has 

 been given. The invention may be described in a few words as being 

 the application of electric light to the Microscope, and the result, so 

 far as the spectacle is concerned, is a sort of improved and enlarged 

 magic lantern. Every one is familiar with the former exhibitions at 

 the Polytechnic and elsewhere of the animalculse (sic) in a drop of 

 water, magnified and thrown, by the aid of the lime-light, on to a 

 white screen. Precisely the same sort of effect was produced on 

 Saturday by Mr. F. Link, the London agent for Messrs. Bauer and 

 Co., with this difference, that the magnifying power was enormously 

 in excess of that attained in the old magic lantern entertainments. 

 The electric Microscope has, in fact, made it possible to exhibit in a 

 most attractive form, the appearances presented by minute natural 

 objects when placed under the most powerful magnifying glass. 

 Indeed, the difficulty with which Mr. Link had to contend on 



* ' Morning Post,' 5th Jan., 1884. 



