Lampbrush chromosomes which are chromosomes in meiotic pro phase with laterally projecting loops, have been observed in oocyte nuclei of several vertebrate, some invertebrate species, and in spermato cyte nuclei of Drosophila species. Especially large lampbrush chromo somes occur in oocytes of the urodele Amphibia and in spermatocyte nuclei of Drosophila hydei and some other species belonging to the hyde i subgroup. In Amphibia the premeiotic chromosomes show a chromomeric organization and a pair of lateral loops projects from each chromomere. Often the loops show a thin axis and a matrix...