Ultrastructure of Nucleoli in Oocytes of Patella coerulea

Abstract

A SPECIAL nucleolus, called ‘Primärnucleolus’ by Jörgensen¹, is always present during the growth of oocytes of Patella coerulea, while other nucleoli, called ‘Amphinucleoli’ by the same author gradually make their appearance. The ‘Primärnucleolus’ stains² red with Mallory's method and does not show the nucleolonema of Estable and Sotelo³, while the ‘Amphinucleoli’ stain red at first, become blue later, show nucleolonemal elements and finally adhere to the nuclear membrane, where they gradually disappear. Previous research⁴ suggested that this transition from red to blue might be due to a passage from a dense to a fluid state, which allows nucleolar substances to pass the nuclear membrane. No explanation was given of the presence of the nucleolonema in amphinucleoli and of its absence from the primary nucleolus. Electron microscope observations have been undertaken in order to check these results.