MILIOLIDAE - Acta Palaeontologica Polonica

8 EWA LUCZKOWSKA
Studies of morphological variation in some species, their ontogeny,
differentiation of generations, etc. were carried out on transverse sections
showing the proloculus and successive developmental stages. For example,
the juvenile form of the genus Quinqueloculina generally occurs in
a normal quinueloculine form, whereas the mature stage has a massiline
form and is usually included in the genus Massilina. The sections of these
massiline specimens exhibit the form of the quinqueloculine stage
characteristic of each species.
The most time-consuming job was the grinding of specimens in order
to obtain transverse sections. This was, as a rule, done by the modified
method described by Bogdanowich (1952, p. 49). The consecutive manipulations
were as follows:
1) A drop of liquid Canada balsam was placed on a slide, there being
usually 10 slides in a series.
2) The slides with balsam on them were put in a thermostat for the
balsam to attain the desired density.
3) After the removal and cooling of the slides up to the complete hardening
of the balsam, one specimen was placed on each drop.
4) The balsam was melted in the place where the specimen was positioned
by means of an electrically heated needle and the specimen stuck to it
immediately. The specimen was set in the desired position by suitable
manipulations of the heated needle, attached by its base only, and covered
all over with a thin envelope of balsam. Mounted in this way, it projected
above the surface of the hardened drop and could be ground down easily
and quickly, there being no need to grind off the whole surface of the
balsam, which takes very much time.
5) Grinding was done under a binocular microscope, which afforded
possibilities for constant visual check-up. The slide with a specimen was
(pla.ced on a glass support, equal to it in area and at least 5 mm thick
(e.g. three slides put together) to keep the specimen at a certain distance
from the stage of the microscope and thus to facilitate the movements of
the hand at the time of grinding. Next a drop of water or glycerol and
a little abrasive dust were placed on a slide of frosted glass, the slide was
turned its frosted side down and the specimen, watched under the microscope,
was ground with circular movements, from the top down to the
proloculus. Frosted glass wetted from below is transparent and makes it
possible to watch the procedure all the time. The nicety of movements
and some skill are indispensable, since an excessive pressure exerted on
the specimen may cause its destruction; as a result, however, we
obtain a transverse section of the specimen unfilled with balsam and
therefore more distinct and easier to draw or to take a photograph of.
Nevertheless, with respect to very small and fragile specimens, it is
advisable to fill the chambers with balsam, which can be accomplished
by nearing the electrically heated needle to the specimen, partly ground