(>X THE PREPARATION OP DlATOMACEA!. 



NDER the above heading, Christopher 

 Johnston, M. IX, has published a very 



excellent article,-- to which the follow- 

 ing paper is intended as a supplement, 

 and I know of no better guide for the 

 student. What I have to say 

 the rapid preparation, from crude ma- 

 terial, where this has been at all care- 

 fully gathered, and to a mode of 

 mounting, invariably on the cover of the 

 slide, not mentioned by Dr. Join- 

 but which has some great advant 

 The gatherings should not be dried, 

 but kept moist, in phials, with a little 

 creosote to prevent mould. I very 

 much prefer to examine whole frustules, 

 with both valves adherent, or if filamentous, still cohering. 

 And I have many bottles of preparations for mounting which 

 are nearly as ''lean as though they had been treated with acids. 

 And many of the most interesting pieparations which I 

 Were never boiled in acids. Of course, very much depends 

 upon the skill and carefulness of the gatherer, and a little 

 patience and judgment will enable any one to obtain the crude 

 material tolerably pure. Only a few daw I made a gather- 

 ing of Nilzschice, in which I have the frustules almost 

 from foreign matter as though they had passed through the 

 most elaborate acid and chlorate of potassa treatment. 



Supposing, then, that one has before him a phial which will 

 hold a considerable quantity of water compared with the sedi- 

 ment in it, the latter composed more or less Ol diatoms. We 



riot* tl <>n preceding paj 



