1. Department of Molecular Embryology; Institute for Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg; Albertstrasse 17 D-79104 Freiburg Germany
2. Department of Neuroanatomy; Institute for Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg; Albertstrasse 17 D-79104 Freiburg Germany
3. Department of General Zoology; FB Biology, University of Kaiserslautern; P.B. 3049 D-67653 Kaiserslautern Germany