H. MORLAND ON MOUNTING DIATOMACE.E. 329 



out as a suggestion ; my objection to this plan is that I would 

 be unable to observe the process of fixing clown under the 

 microscope. 



I have occasionally exhibited slides at this Club with one of 

 the diatoms, a very thin one, standing on its edge and perfectly 

 perpendicular. Xow this must appear to many to be extremely 

 difficult of accomplishment, and many may wonder how it is 

 done. The task is not so difficult as it may at first sight appear ; 

 the diatom " on edge " is the first one put into position ; it is 

 by no means difficult to get such a diatom set up on edge some- 

 ivhere near the centre of the cover-glass, but it would be difficult 

 to place it in a certain exact spot, though even this could be 

 done by repeated trials. However, the diatom having been 

 placed on its edge somewhere near the desired spot, the same is 

 now fixed by breathing very, very gently through the " breath- 

 ing tube " with the mouth open. As soon as it is seen that the 

 diatom has got fixed to the cover-glass it must be noted if it be 

 perpendicular or not, if not, it can be set up properly by turn- 

 ing the leaning side towards the end of the " breathing tube" 

 and blowing it over gently, the breath softening the gum to the 

 necessary pitch. In such a slide only one diatom is fixed up " on 

 edge," the remaining valves being afterwards added, laid 

 flat, 



In drying cleaned material on a glass slip, it will often be 

 found that the surface of the glass appears as if it were greasy, 

 causing the water to run up into very irregular shapes with the 

 diatoms all in patches. This is very annoying when diatoms 

 are particularly wanted to be spread as evenly as possible, but 

 the difficulty is easily overcome ; all that is necessary is to take 

 a drop or two of clean water and a clean cloth and rub the sur- 

 face of the slip, but not quite dry, the residue of moisture being- 

 allowed to evaporate spontaneously ; if properly carried out this 

 plan will now allow the water with cleaned material to lie on it 

 in any manner desired. Should the cloth leave any fibres behind 

 they must be removed with a camel-hair pencil. The slip must 

 not be rubbed again with the cloth when once it has dried, as it 

 is the dry cloth which seems to impart the greasiness to the 

 surface of the glass. 



Although I have mounted diatoms for some time past, I don't 

 find that I can now prepare them any the quicker, the fact 



