48 CULTIVATION OF DIATOMS. 



A short filament of Zostera is added to it for organic nutriment. 

 The water which has evaporated should of course be made up by 

 adding sterilised distilled or rain water. 



Many diatoms, both marine and fresh water, require a special cultiva- 

 tion. 



It is evident that in this summary we are unable to enter into these 

 details and we therefore refer the reader to the original papers by 

 Dr. Miquel, published both in Le Diatomiste and in the Annalcs de 

 Micrographie. 



C. Pure Cultivation of Diatoms. 



These cultivations are much more difficult than the preceding. In 

 the first place a thoroughly healthy and fresh diatom should be isolated, 

 which may be effected either by isolating it in the medium in which it 

 is found by various artifices (capillary tube, pipette, hog's bristle, &c), 

 or by breaking up the said medium after the fashion of Bacteriologists. 

 As a rule it is by this last method, which is unfortunately rather lengthy, 

 that an ordinary gathering can be turned to the best account. 



It is well known that this breaking up ( J ) is effected by mixing for 

 example one drop of diatomiferous liquid with iooc.c. of nutrient liquid 

 and by again diluting i c.c. of the resulting liquid in 09 c.c. of fresh 

 liquid. This last-mentioned liquid is then apportioned for example in 

 10 Frendenreich flasks and submitted to cultivation. 



If the last liquid thus obtained be still too rich (i.e., contains many 

 kinds of diatoms) it should be diluted a third and, if necessary, a lourth 

 time. 



In this way cultivations in which not more than a single form occurs 

 and from which subsequent cultivations can be made will eventually be 

 obtained. These cultivations which we shall call Research Cuitira/ions, 

 can be made in various ways. One of the most interesting is cell 

 cultivation originated by Dr. Miquel, and described by him in 

 " L'Annuaire de l'Observatoire de Montsouris," 1892-1893. 



The cells of Dr. Miquel are constructed as follows : 



" A cell is cemented, without solution of continuity, to a glass slip, 

 near the upper edge of which is bored an aperture about 2mm. in 

 diameter, and over this cell is similarly cemented a thin circular cover- 

 glass. In this way an entirely new kind of cell is produced, having 



( r ) See Manuel d'analyse bactriologique des eaux par le Dr. P. Miquel. Paris, Gauthier 

 Villars, 1892. 



