Article révisé par les pairs
Résumé : Eggs of Rutilus rutilus at different stages of development have been observed in the S.E.M. after fracturing and dissection. The observations have shown: the particular structure of the yolk as seen in fracture; the incompletely segmented blastomeres fusing in, and increasing the syncytial layer during the early stages of cleavage; the morphological differences between the cells of the enveloping layer and the various kinds of deep cells (central, marginal, bottom cells) at the different stages. These differences give indications about the relative mobility and the degree of adhesiveness of the different cell types. Our morphological observations are in good agreement with experimental and ultrastructural data reported by other authors on the species Fundulus and Salmo.