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

Open Access
Publisher Website
Google Scholar
Abstract
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.