[Protein incorporation pattern in early organogenesis ofDermestes frischi (coleoptera)].

1. Tritium-labelled amino acids were injected into the yolk system of theDermestes egg in order to analyze the protein metabolism during early differentiation of the embryonic germ layers and to prove whether the differentiation pattern in early organogenesis corresponds with the uptake of radioactivity. 2. Before germ anlage formation the radioactivity is incorporated homogeneously in all superficial cell regions (Abb. 1), but with the separation of the embryonic blastemas just prior to the invagination of the middle plate the presumptive serosa is excluded from the uptake ofH-labelled amino acids. Only in amnion development do regions of the cellular protective membranes which cover the germ band incorporate radioactivity especially in the nuclei (Abb. 2c). 3. During the formation of the inner germ layers and the following development of coelomic sacs from middle plate material and of ventral nerve cord from the ectoderm, the incorporation of radioactivity into the embryonic blastemas continues. But now it is much more intense in ectoderm cells (Abb. 2e). These results indicate that the differentiation processes are probably further developed in the ectoderm than in other embryonic blastemas in agreement with studies on the developmental potencies of germ layers which are discussed. 4. Besides the uptake of radioactivity into the cytoplasm of the embryonic cells a specific incorporation of theH-amino acids into the nuclei has been observed. When the tracer was injected at an early stage of germ band formation offering the labelled amino acids for a long period in development the radioactivity accumulates in a small zone surrounding the membranes of the nuclei (Abb. 2d, g). It is assumed that in this region specific incorporation of radioactivity could be a visible indication of cell differentiation in early organogenesis.