244 



THE CULTIVATION OF DIATOMS 



You prepare in advance fifty or sixty vessels, half full of nutri- 

 tive liquid, perfectly sterilised, and you adopt, in order to facilitate 

 the operation, flasks of a medium size, capped and tubulated, of 

 the shape recommended by my friend Freudenreich. 



As a rule, the bacteria that are found in cultures of diatoms, 

 from which the green algae, the fungi, and the protozoa have been 



TM 



Fig. 64.— Apparatus for separating Diatoms from Bacteria. R, the flask ; 

 T', a tube making the communication between the flask and the 

 atmosphere ; h, a tuft of wadding ; r, stop-cock ; T, a tube conduct- 

 ing the water that has been sterilised by filtration ; T\ a siphon with 

 a stopcock, r ' ; and V, a receiving-vessel, with an outflow, Z, to 

 maintain a constant level. 



eliminated, are in far greater number than the diatoms. The 

 operation of separation is not practicable directly, and you can 

 only make use of it after you have got rid of the greater part of 

 the bacteria. These infinitely small creatures, being more capable 

 of resisting the action of heat and all other destructive agents, the 



