1. Strains of epithelium and fibroblasts cultivated side by side in the same medium keep their individual characteristics. When sectioned and stained by the Van Gieson method, the cultures show the epithelium stained greenish yellow and the fibroblasts and their fibrillæ pink.
2. There are no transition forms between the epithelial cells and fibroblasts.
3. The epithelial cells belonging to an older strain are still able to form primitive structures of winding tubules, with typical glandular epithelium.
4. Under the conditions of the experiments, no dedifferentiation takes place.