318 



Notes on Mounting the Diatomace^e. 

 By H. Moeland. 



{Read November 23rd, 1888.) 



As far as possible it is my intention in this paper to confine 

 my remarks to the preparation of diatom slides and to the 

 means as adopted by myself ; I shall therefore have nothing to 

 say about the preparation of the material, whether from recent 

 gatherings or from fossil deposits, nor shall I have any remarks 

 to offer about mounting in media of which I may only oc- 

 casionally make use. 



The media I usually employ are either air, Canada balsam, or 

 the so-called styrax, and I mount my diatoms either " spread " 

 or " selected." 



Mounting slides of " spread ' diatoms is simplicity itself, 

 but, for all that, there are immense quantities of such slides 

 prepared which are very far from being what they should be, 

 the fault in no way lying with the cleaning of the material but 

 in the way that the same has been mounted. 



For instance, we will take a slide mounted " dry ; ' in many 

 cases such a slide will be found to have either one or other of 

 the following faults : — lstly. The diatoms have dried in ridges. 

 2ndly. The cell is so shallow that the slightest pressure on the 

 thin cover-glass either crushes the diatoms between the same 

 and the slip, or transfers it from the former to the latter, and 

 3rdly. If the slide be an old mount, in far too many cases the 

 underside of the cover-glass is " dewed." 



Now all and each of these faults are avoidable, and with 

 very little trouble, nor is any particular skill required, though 

 certainly a little judgment, easily acquired after but very short 

 practice. 



My method of preparing a " dry ' mount is as follows : — 

 First of all, I have ready prepared a number of slips with rings 

 of either Bell's cement or Hollis's liquid glue (the former pre- 

 ferable, being cleaner) traced on them ; these cement rings are 



