Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 50. (Budapest 1958)

M. Nyírő, R.: The studying of Foraminifera in thin sections

The Studying of Foraminifera in Thin Sections By RÉKA M. NYÍRŐ, Budapest There was no systematic investigation regarding thin section studies of Foraminifera in Hungary up to now, though to study specimens in thin sections is important for several causes. The main points of view are : 1. The knowledge of the internal structure of Foraminifera ; 2. The comparison of external features and internal structure ; 3. The comparative studies of the internal structures of the species ; 4. The comparison of Foraminifera of a known internal structure with the micro-fauna of unsluiceable rocks. At first, the study of thin sections of Foraminifera characteristical of the several stratigraphic units seemed to be suitable. Later, however, it was found to be more expedient and fruitful to switch investigations over on a systematical base, that is, the comparison of species and genera within the frames of a family. This paper was yet prepared on the base of the first conception. The history of research methods and directions is as follows. With the exception of Nummulines, we meet but rarely in literature with thin section studies of the minute Foraminifera. Contrarily with Nummulines namely, to study sections of the small sized Foraminifera one has to have a suitable method of microtechnique. Hoher experiments with Canada balsam in 1933. D u m b a r t and H e m b e r t use a bakélite impregnation for the cutting of thin-shelled specimens. Glaessner (10) continues to use Canada balsam, yet, at the same time, mentions the successful application for the sectioning of harder samples the cement" prepared by Rosenbusch (ingredients : 50% shellac 50% paraffine). Stach (28) uses the so-called „Schneide höhn" resin for the calcareous Foraminifera. His method, however, is not suitable for the arenaceous forms, since this resin wears out speedily and the harder shell cracks away. Emiliani (9) recommends an imbedding material called thermoplast, worked out by Meyer and Levinson. Its drawback is that this material is applicable only about 80° C, and so the imbedding is very complicated. Beckmann (4) advises shellac as an imbedding material, and Z e i d 1 e r (4) tooth cement instead of the obsolete Canada balsam and paraffine imbedding methods. K r e m p and J o h s t (20) are also against the use of the Canada balsam and paraffine method expounded by Glaessner (10), since they found it unsuitable for the imbedding of fossils with a harder shell. The same as Beckmann, they too apply the shellac imbedding. K r e m p (19), when treating the thin sectioning studies of microfaunas from the Carboniferous, calls attention to learn the internal structure of arenaceous forms. Hagn (11, 12, 13, 14) recommends the use of a honey-like polyester resin, applicable without heating also on room terqperature. As a preparation, he steeps the thin and fragile -pecimens in shellac or Canada balsam until they reach the necessary hardening. Hagn considers the sectioning school especially important for the study of Globotruncanas and arenaceous forms. He emphasizes the necessity of collaboration and close connection of the workers in this field for the sake of development of microtechnique methods and research directions.