The annulate lamellae of chick embryo liver cells in organ culture

Cytoplasmic annulate lamellae are described as occurring in the cells of chick embryo liver during raft‐type organ culture on Eagle's minimum essential medium. These transitory structures, prominent in the cells of early (5‐day) embryonic liver during culture, were closely associated with the outer nuclear membrane and mitochondria, and were frequently continuous with portions of the rough endoplasmic reticulum. In contrast, annulate lamellae were not found in any cell examined during organ culture of older (11‐day) embryonic liver. These observations, together with correlative enzymatic studies, are discussed with regard to the possible role of annulate lamellae in the differentiation of the liver cell, in the light of current hypotheses on the origin and function of these widely‐occurring organelles.