The paper reports the results of organogenic and histogenic investigations of the visceral organs of embryonic Japanese quails incubated in the microgravity aboard orbital complex Mir. Investigations of the gastrointestinal tract failed to reveal macrodeviations in the organs' structure, differentiation of layers or cells along the full length of the entodermal canal. However, comparison with the ground controls exhibited poor development of stromal connective tissues in the flight embryos evidencing loose arrangement and small number of fibers. Local hyperplasia in the duodenal epithelium was due to the proliferation rather than differentiation processes; it could affect food intake and parietal digestion in the flight chicks. Though the Japanese quail embryos developed in space microgravity had some deviations, their digestic apparatus was mature to uptake and assimilate food.