Ovarian oocytes of the three fresh-water Triclads: Planaria torva, Dendrocoelum lacteum and Polycelis nigra have been studied by means of histochemical and electron microscopical techniques. Prediplotenic oocytes seem alike in all species and their cytoplasm is characterized by a high content of RNA. During diplotene, small bodies (less than $1\mu$ in diameter) begin to appear mainly at the periphery of the cytoplasm. They look the same in P. trova and in D. lacteum, whereas they are of a different kind in P. nigra. Nature and function of these bodies have been discussed in relation to the problem of yolk and cortical granule presence.
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Con il contributo del Ministero per i Beni e le Attività Culturali