The Lampbrush Chromosomes ofRana EsculentaL. (Amphibia — Anura)

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Abstract
The lampbrush chromosomes from oocytes of Rana esculenta L. have been observed by phase contrast microscopy. The lengths of the thirteen lampbrush chromosomes have been calculated by the averages of the length of each chromosome in the nine oocytes observed, in relation to the length of bivalent XIII taken as 100 units. Several landmarks such as spheres, dense matrix loops, giant structures and globules were observed. Their position and the relative length allowed the identification of the single chromosomes. Spheres, situated on bivalents VIII, X, XI are spherical in shape and with a smooth outline; under phase contrast, they appear like bright, homogeneous objects, displaying various numbers of vacuoles. Spheres on bivalent II are smaller and appear opaque and without vacuoles under phase contrast. Dense matrix loops are lateral expansions coated with a dense matrix. They show an irregular outline and appear homogeneous under phase contrast. Giant structures present an aspect varying from one oocyte to another; they are sometimes spherical and sometimes ring shaped owing to a large central vacuole. Several free nucleoli were observed in the nuclear sap, in peripherical position in relation to the chromosomes. The centromeric regions were not morphologically detectable, and were determined by a statistical study of distribution and frequency of chiasmata.