Publications

The present report deals with several problems concerning the Chitinozoa. The wall of Cyathochitina campanulaeformis proves to be single-layered, in contrast to the often expressed opinion that the walls consist of two layers.

It is supposed that all Chitinozoa, even those always found single, originate in chains. But the formation of these chains and their direction are far from being understood. According to Eisenack, 1968, a part of the living content of a test penetrates through a pore of the aboral pole, extends further and forms the test of the next chamber. According to Cramer, 1970, the test stretches, swells by taking the shape of a whole chamber, and is subdivided. This may occur within a chain, thus causing it to become longer. The Baltic associations, which have been studied over 40 years, have yielded only 3 specimens which seem to support the view of Cramer. Both views, however, are not yet proved.

The so-called Opistosomes, dark bodies situated in the interior near the aboral pole, proved to be folds caused by pressure. They have not been found constantly, and only in specimens from shady silty sediments.

On the other hand, spherical bodies with thin walls and situated more centrally, had been observed in a few cases. The author takes these for the exceptionally chitinizied principal contents, the mesosome. This view is in accordance with the assumption that the Chitinozoans have been tests of eggs or larvae.

The next section deals once more with the variability of some species. It is shown that in simple forms the neglect of a study of their variation may lead to confusion. In this connection, a new species is established, Eisenackitina elongata, a close relative of Bursachitina bohemica.

No conformity has been reached till now as to the supergeneric subdivision of the Chitinozoa. Taugourdeau, 1966, subdivided the Chitinozoa into Copulida and Acopulida, not considering the variability of the copula which is caused by the difference in the degree of its chitinisization. The copula may be reduced completely in forms where it is present normally. Vice versa, the copula may occasionally occur in the Acopulida.

Jansonius, 1970, subdivided the Chitinozoa into Simplexoperculati and Complexoperculati, of which the first group has an operculum in the aperture or somewhat deeper in the shell. The second group has a more complex operculum now called prosome. However, there is no clear difference between a deep operculum and a prosome. Eisenack, 1968, 1972, proposed a subdivision into Operculifera and Prosomatifera. In the Operculifera the aperture is closed by a lid (operculum) whereas in the Prosomatifera the test is closed by a nearly cylindrical plug (prosome) which is situated in a distinct distance from the aperture, mostly at the boundary between the neck and the main-chamber, or in cylindrical species, in a comparable distance. However, there arises the question whether a (reduced?) lid may be present in addition to a prosome. Some features seem to indicate such a possibility.