Full set of lampbrush chromosomes from P. ridibundus (the lake frog) oocyte. Oocyte chromosome set consists of 13 lampbrush stage bivalents with 5 large lampbrush chromosomes and 8 lampbrush chromosomes of smaller size. Lampbrush chromosomes were lettered according to their comparative size. Phase contrast micrograph. Nu – extrachromosomal and chromosome associated nucleoli. Scale bar = 50 μm.