G8 
Journal of the 
mounting the two species common in the West Melbourne swamp* 
deposit, T hit upon the following plan, which proved perfectly 
effective. A very small drop of balsam is placed in the centre of 
the slide, and made very thin with carbolic acid—turpentine will 
not answer, as it spreads all over the slide. The point of the 
needle is dipped into this and held in readiness while the material 
is undergoing examination. When a good specimen is found it is 
removed on the balsamed needle-point, and the prepared slide 
being placed under the microscope the diatom is deposited in the 
thin balsam, washed in it, and pushed into the centre of the field. 
After a sufficient number of diatoms have been arranged in this 
manner, and any extraneous matter removed with the needle 
point, the slide is to be heated over the lamp till the balsam, on 
cooling, becomes hard and firm. A small drop of soft balsam is 
then let fall on the diatoms and a covering-glass applied, the 
diatoms not being disturbed, owing to their being firmly imbedded 
in the solidified balsam. The security from disarrangement 
afforded by this method is often highly advantageous; for 
example, we may have only two or three valves of a particular 
species, and each valve may differ from the others in outline or 
markings, as in the number of rays in a Ileliopella or A ulacodiscus, 
or in the shape of different specimens of Navicula Smithii from 
the West Melbourne deposit, and many other variable species. Or 
again, they may present the extremes of size found in the species, or 
various stages of self-division, and in any of these cases it is very 
desirable that they should be mounted side by side for comparison; 
but if mounted in the manner first described there is always 
more or less liability of their being scattered, and the process just 
mentioned is, I think, the simplest Way of avoiding this result. 
A^ain, it will sometimes he found difficult to make the diatoms 
adhere to the needle by simply moistening it, the flat ones 
especially being often crushed in the attempt; and when they do 
adhere they are liable to fall off the needle while the slides are 
being changed, which latter accident is peculiarly annoying, as the 
largest and finest diatoms are, from their weight, the most likely 
to be lost. By using a needle dipped in thin balsam they are far 
more easily taken up, and the danger of dropping them is quite 
removed. Moreover, by observing the valves in balsam before 
