Embryogenesis of Calliphora Erythrocephala Meigen. Ii. Glycogen Pattern

1. The glycogen patterns of most of the organs of Calliphora erythrocephala during embryological development are described. In the early embryonic period no distinct increase or decrease is seen in the glycogen content, but a shift in the localization of the glycogen is found. A glycogen-rich peripheral zone is formed in the yolk mass. After the formation of the first organ rudiments, slight differences in glycogen level and localization appear. Only the pole cells show an unequivocal chemodifferentiation, losing their glycogen completely. 2. During differentiation into functioning organs, three glycogen patterns are found: a) Stores are accumulated and then consumed partially or completely. b) Stores are formed but not consumed during subsequent embryonic life. c) No glycogen is stored and the amount already present is consumed. The possible functions of glycogen are discussed. The glycogen initially stored during oogenesis probably serves as energy supply. The storage of glycogen during the mid- and late embryonic periods provides a large supply on the spot for production of precursors of glucose derivatives. All chitin-synthesizing organs store glycogen and use it partially or completely. Cells that have to produce a large amount of chitin, e.g., pharyngeal and proventricular cells, store relatively most of the glycogen. Cells destined to produce large amounts of mucopolysaccharides, e.g., those of the PMP, store more glycogen than cells which, like the AMP, form smaller amounts of mucopolysaccharides. 3. A glycogen stock could be formed along two pathways: the interconversion of lipids into carbohydrates and/or the de-amination of proteins.