82 PREPARATION OF DIATOMS. 



" These operations take longer to describe than to carry out and a 

 large number of types may be prepared in a very short time. 



" If one wishes to place but one to three specimens on a cover- 

 glass, it is better to fix them as I have indicated above. If, on the 

 contrary, it is desired to arrange a larger number of individuals seriatim, 

 it is preferable to previously coat the cover-glass with a layer of gum. 



" It is useless to trouble one's self about the appearance of the 

 diatoms before the balsam has been applied, because the gum (unlike 

 gum arabic) subsequently becomes quite invisible." 



