Cleaning and Mounting Diatoms, etc. 207 



to settle before pouring off the water. In this way all 

 soluble impurities can be removed. When the water 

 remains clear, pour it off, leaving the diatoms as nearly- 

 dry as possible, and cover them with strong alcohol, which 

 will extract the endochrome ; change the alcohol daily until 

 it ceases to be tinged with green ; then wash away the 

 alcohol with water, pour off the water, and place the 

 diatoms in a platinum capsule and heat them to a dull red 

 over a spirit-lamp. This will separate the frustules into 

 single valves, and finish the cleaning of the diatoms, and 

 they may then be bottled up in distilled water. 



To Clean Polycystina. — The polycystinous earth should 

 be broken into small pieces and boiled for several hours in 

 a strong solution of common washing soda, the disinte- 

 grated matter being from time to time poured off into a 

 vessel, and the boiling in soda continued until all the earth 

 is broken up. Wash the disintegrated matter in water 

 several times to remove the soda, allow the polycystina to 

 settle down, and pour off the water and place the forms in 

 a test-tube ; add some nitric acid, and boil for twenty 

 minutes. Eemove all trace of acid with water, and bottle 

 up in distilled water. 



To Clean Foraminifera. — All mud must be got rid of 

 by repeated washing in water. Then boil the forms in a 

 strong solution of bicarbonate of soda for an hour or two. 

 When clean, wash away the soda, and bottle in distilled 

 water. 



To Mount Diatoms in Canada Balsam {Unselected 

 Slides). — The diatoms are to be taken out of the bottle with 

 a dipping-tube, and should be allowed to fall upon a clean 

 cover-glass. The fall of the drop causes the forms to 

 spread evenly over the cover. It should then be dried 

 slowly over a spirit-lamp. When dry a small drop of 

 Canada balsam is to be applied, and the slide put away out 

 of reach of dust to dry for twelve hours. Now place on a 

 hot plate, and apply gentle heat from a spirit-lamp for 

 about ten minutes. Allow it to cool. Take the cover 



