Scanning electron microscopy of Drosophila embryogenesis: 1. The structure of the egg envelopes and the formation of the cellular blastoderm

As part of a series of detailed observations on embryogenesis in Drosophila, the protective coverings of the egg and surface changes in the embryo prior to gastrulation have been studied with the SEM. Four specializations of the chorion are described: the plastron, micropylar cone, operculum, and the posterior thickening. After removal of the protective coverings the surface changes during development can be observed. During the first eight synchronous nuclear divisions a dense array of thin microprojections covers the whole embryo. After the ninth division between 373 and 408 nuclei reach the surface and become located in cytoplasmic projections. From counts of the number of surface bulges during the syncytial blastema stages, it was established that 13 synchronous divisions take place producing between 5600 and 6500 surface nuclei. During formation of the cellular blastoderm, the location of the prospective cells becomes obscured by a dense pattern of microprojections from each cell. However, with the completion of the blastoderm, the surfaces of the cells become smooth and the cell outlines distinct. The usefulness of the SEM in developmental studies is discussed.     

Ein Fall von zweikieligem adossiertem Vorblatt beiSwertia perennis L

Ohne Zusammenfassung     

Die bodenfauna des greifswalder boddens. Ein beitrag zur ökologie der brackwasserfauna

Ohne Zusammenfassung     

Die Wirkung von Licht auf den Transport von 2-[14C]Abscisinsäure in Bohnenwurzelsegmenten

Summary Light promotes the acropetal movement of 2-[¹⁴C]ABA through root segments of Phaseolus coccineus L. The promotion occurs only when the segments are irradited during the transport period. Red light and blue light are as effective as white light. There is no significant promotion when the segments are irradiated with green light or when they are kept in darkness during the transport period after preceding light treatment. Light has no effect on basipetal ABA-transport.

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Abkürzungen ABA Abscisinsäure - D Dunkel - GA Gibberellinsäure - IAA Indolessigsäure - L Licht - PPO Diphenyloxazol     

Additions and corrections to “The Muscidae of Central Europe” II. Two new species of Spilogona (Diptera, Muscidae)

Two species of Spilogona, S. angustigena sp. n. and S. tatrica sp. n., are described from the Czech Republic and Slovakia, respectively. Both species are characterised by a gynaecomorphic shape of the male head, i.e., by a broad frons and the presence of a pair of orbital setae. Three species with this type of head are already known in the Palaearctic region: S. karelica (Tiensuu, 1935) from Russian Karelia, S. lapponica (Ringdahl, 1932) occurring in Norway and Sweden and redescribed here from material collected recently in Russia and Sweden, and S. spinicosta (Stein, 1907) from Tibet. All five species are compared and a new identification key is given. Apart from the external similarity of the male heads, the species under study are hardly closely related and their dichoptic heads may be explained as a homoplasy among similar ecomorpha.