[Cytochemical and ultrastructural study of oogenesis inLithobius forficatus L. (Myriapoda, Chilopoda). Evolution of cellular components].

The development of the oocyte takes place in four classical phases: premeiosis, previtellogenesis, vitellogenesis and maturation.During previtellogenesis, nucleus and cytoplasm grow considerably. The nucleolar material breaks up into numerous masses and laminae and nuclear extrusions are very frequent. The number of ribosomes and mitochondria increases markedly; the mitochondria show pronounced morphological modifications: stacking, honeycomb-like figures. Lysosomal formations are numerous.During vitellogenesis, the nucleus shows little activity and yolk accumulates in the cytoplasm. The number of ribosomes and mitochondria decreases. During maturation, the Golgi apparatus seems to bud off vacuoles in the cortical cytoplasm.Cytological and cytochemical modifications are discussed in relation to the physiological development of the oocyte.