44 THE ORIGIN OF LIFE 



there they may be found much more easily in the 

 small than in the large amount of deposit. 1 



In regard to this latter point that is, the 

 finding of organisms when the deposit is con- 

 siderable it is often a matter of great difficulty, re- 

 quiring much time and patience. If they are very 

 abundant, they may be found readily in the first 

 sample of the sediment taken with a sterilised 

 pipette from the just opened tube. But at other 

 times, when present only in small numbers, two 

 or three samples may have to be examined and 

 one or two hours spent, with the light carefully 

 adjusted, before any of the sparsely distributed 

 organisms can be discovered. 



Again, even the organisms most commonly met 

 with, the Toruke, are often extremely minute (see 

 Plate 3, Fig. 14), and thus difficult to be found 



1 In these tentative trials it is best to use thoroughly steril- 

 ised two-ounce flasks, subsequently fitted with previously boiled 

 india-rubber stoppers, having in each a small wedge-shaped 

 portion cut out of its lower extremity, so that the stopper when 

 loosely standing in the neck of the flask may allow of the pas- 

 sage of the steam, and yet when the ebullition has ceased may 

 permit of the flask being securely closed. And in the prepara- 

 tion of these solutions, when small quantities only are often 

 required, it is best to use a dropper. With that which I have 

 always employed 40 drops equal 36 minims of the dilute sodium 

 silicate, 38 minims of the dilute phosphoric acid, and 40 minims 

 of the liquor ferri pernitratis. In preparing the colourless solu- 

 tion it is best to dissolve the ammonium phosphate first, then add 

 the acid, and lastly the dilute sodium silicate. 



