208 THE ENTOMOSTRACA OF EPPING FOREST.
live-box to a compressorium, because with the former it is
possible with a little practice to so manipulate the lid that an
animal can be turned or rolled into almost any desired
position.
The best means of preserving collected material and selected
specimens is still somewhat of an open question. Numerous
liquids and solutions have been tried with varying degrees of
success or the reverse, but there are only two which, by reason
of their simplicity in application and inexpensiveness, need be
mentioned here. Some of the most experienced workers
consider that, in spite of its many shortcomings, such as its
rapidity of evaporation and the darkening and contraction which
it produces, alcohol in some form is still the best all-round
preserving medium. If mixed with a little glycerine the chances
of complete evaporation may be very much reduced, and some
further slight advantages obtained. Next to spirit may certainly
be placed the comparatively recent introduction, Formalin
(solution of Formaldehyde). This is especially useful in cases
where it is desired to preserve something of the original
transparency of the animals. It is also very valuable on
account of its efficacy in extremely weak solutions, a few drops
at the ordinary strength as sold (40%) being sufficient, for a time
at least, for the preservation of quite large collections. The
mounting of Entomostraca on glass slips as permanent
microscopic objects, although it can be pretty satisfactorily
accomplished in glycerine jelly and similar media, has very
little to recommend it to the busy student. The method
of putting selected specimens into spirit or 5% formalin
in little corked tubes (11/2" x 3/8" are large enough in
most cases) is not only much simpler, but also allows of the
animals being examined in any desired position. Necessarily
for this purpose the latter have to be picked out with a fine
pipette and placed in a live-box or similar object-carrier, but
this can be done very rapidly and without any difficulty.
Literature.3
One of the greatest difficulties to the beginner in the study
of the Entomostraca is in connection with the literature, which,
to say the least of it, is somewhat scattered. A few words on
3 As stated in the foot-note at the commencement of this article, a Bibliography of the
books and papers relating to the British Fresh-water species will form Part IV. of this
paper.—Ed.