The effect of removing the polar lobe in centrifuged eggs of Dentalium

Classical evidence for the existence of morphogenetic substances was provided by experiments with spiralian eggs possessing a polar lobe: Ilyanassa (Crampton, 1896; Clement, 1952, 1956, 1962); Dentalium (Wilson, 1904); Chaetopterus (Tyler, 1930); Sabellaria (Hatt, 1932; Novikoff, 1938); and Mytilus (Rattenbury & Berg, 1954). Eggs from which the polar lobe had been removed developed into embryos with specific abnormalities. In Dentalium, after removal of the polar lobe at the trefoil stage, a trochophore larva is formed without post-trochal region and apical tuft. Removal of the polar lobe at second cleavage causes a larva without post-trochal region, but with an apical tuft. Wilson concluded that specific cytoplasmic materials essential to the formation of the apical tuft are contained in the first but no longer in the second polar lobe. Centrifuging the uncleaved egg just before first cleavage will disturb the normal distribution of substances.

Über die Beeinflussung artspezifischer Formbildungsprozesse von Acetabularia durch UV-Bestrahlung

The inhibition of morphogenesis in enucleated cells of Acetabularia by u.v. irradiation is due to a destruction of species-specific morphogenetic substances stored within the cytoplasm. The possible relations to the destruction of cytoplasmic RNA are discussed.

Die Wirkung von Strahlen auf Acetabularien

Grafts made of two X-irradiated nucleated cell parts of Acetabularia mediterranea showed about the same dose-dependent reduction of the cap forming ability as previously found for ungrafted uninucleated cell parts. Similar grafts with one irradiated and one unirradiated partner showed no significant reduction of the cap forming ability. Twonucleated interspecies grafts between an irradiated partner and an unirradiated partner, i.e. A. mediterranea or crenulata, revealed both a dose-dependent and irreversible destruction of the species specific morphogenetic substances stored within the cytoplasm and of the nucleus-dependent production of these substances as judged by the morphology of the caps formed by these grafts.