308 On Selecting and Mounting Diatoms. — [wyrens yeree eon 
I1I.—On Selecting and Mounting Diatoms. 
By Captain Frep. H. Lane, President of the Reading 
Microscopical Society. 
Up to the present time a well-cleaned but mixed slide of the diato- 
maces from any particular locality has, as a general rule, been 
considered sufficient ; but though such slides are interesting, and 
in one sense instructive, as showing the prevalent genera and species 
abounding in a stated place, they are, in another point of view, 
unsatisfactory, and teach the beginner little. In the very last year of 
the late Dr. Arnott’s life, I heard him say that were he to commence 
a fresh collection of diatomaceze he would admit none but perfectly 
ure and unmixed gatherings into his cabinet. I was much struck 
with this observation at the time, but reflection convinced me that 
the longest life would not suffice for such an undertaking, as a pure 
gathering is the exception, and a mixed one the rule. The systematic 
diatomist must, therefore, be put to all sorts of straits, and the same 
gathering has to do duty in the cabinet as an example of various 
genera and species; and in many instances the particular species to 
be illustrated, if it is at all a rare one, is almost smothered by the 
commoner and more numerous ones. This is of course a great 
drawback to anyone commencing the study of these organisms ; as 
he is confounded with the multiplicity of almost similar forms, and 
can only with doubt and difficulty identify the one he is searching for. 
But if pure gatherings of all species cannot be obtained, it is now 
comparatively easy to pick out those that are required from the 
general mass; and it is a matter of wonder to me that this has not 
been more generally attempted, for I am not aware of a single col- 
lection of the kind, with the exception of that which Hulenstein is 
now making for his subscribers. Selected diatoms of the more 
showy sort are occasionally to be obtained at the opticians, even 
arranged in patterns as pretty “Oh law” objects for the microscope ; 
but I would fain induce our members, and others also, to isolate and 
mount on separate slides every diatom, common or rare, that is to 
be procured in their own locality, or in gatherings from elsewhere ; 
for if everyone would set to work to do this, we should soon be in 
the possession of a complete series of really instructive slides of the 
diatomacez. 
The object of my paper this evening is not only to insist upon 
the advantages of this plan, but to render the task easier by giving 
you the benefit of my own experience, reaped through many failures, 
in selecting and mounting these exquisitely delicate and beautiful 
forms. 
For a long time I had been content with mounting general 
gatherings, but having received from Liverpool some Californian 
shell cleanings, I was fired with the ambition of picking out the 
