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Qn tbe (Tultivatton of ©iatome b\i artificial 



fIDeane- 



By Dr. P. Miquel. (Translated from La Diatomiste^ 



Chapter II. 

 GROWTH OF UNMIXED DIATOMS. 



WE may consider two methods for the cultivation of unmixed 

 diatoms. The first is one in which one kind only grows 

 and multiplies, to the exclusion of all other siliceous 

 alg£e ; the second is one in which one special diatom is evolved to 

 the exclusion of all other living organisms, \vhether infusoria, green 

 algae, fungi, bacteria, etc. This latter should be called the cultiva- 

 tion of Diatoms in a state of absolute purity. 



If the first of these methods is comparatively easy of success, 

 the second is, on the contrary, very difiicult, which arises, not from 

 the impossibility which is often found of separating the diatoms 

 from the green algae, the fungi, and the protozoa, but from the 

 bacteria that often live as parasites on the exterior thallus of the 

 friistules. 



I. — Growth of One Single Species. 



In order to be assured that you have in any maceration but one 

 species of Diatoms, you may use several processes — some special 

 and not equally applicable to all species ; others are general, and 

 furnish in all cases certain results if they are applied with judgment. 



Special process. — I suppose that it is desired to insulate from a 

 natural or artificial growth, containing numerous species, a fila- 

 mentous diatom of the family of Melosiras. If the filaments of 

 Melosira rise in the liquid above the sediment — which is very 

 often the case — you take hold with tweezers, whose tips have been 

 previously heated, a portion of the filament, which may be visible 

 to the naked eye or may require a lens, and wash it repeatedly in 

 sterilised water, and then quickly, and before it dries, place it in a 

 fresh maceration that has been maintained for a quarter of an hour 

 at 7o^C. and then cooled. 



The washing is intended to detach from the filament, as far as 

 is possible, any other Diatoms that may be adherent to it ; it will 

 not always succeed, as you often find other species grow by the 



