Annulate lamellae in hepatic and pancreatic beta cells of the chick embryo

This study is concerned with the finding of cytoplasmic annulate lamellae in normally developing avian somatic tissues. Annulate lamellae were observed in hepatic parenchymal and pancreatic beta cells of the chick embryo on days five and eleven, respectively, of egg incubation. The presence of this cytoplasmic membrane system in normal embryonic tissues supports the view that annulate lamellae may represent normally occurring, transitory organelles common to virtually all cells during early embryonic differentiation.