The study investigates the retention of differentiation potential in myogenic cells during prolonged in vitro cultivation. It was hypothesized that if differentiation depends on preformed informational molecules, continuous multiplication would lead to loss of this potential. Cultures of skeletal muscle cells from newborn rats were studied, showing that myoblasts divide and then fuse into multinucleated muscle fibers. Experiments demonstrated that myogenic cell lines could be maintained for many months without loss of differentiation potential. Cloning experiments showed that the potentiality to differentiate is inherited by virtually all cells. The results indicate that cells maintained in exponential growth can pass on their capacity to fuse and differentiate into muscle fibers. The study also shows that myogenic cells can be maintained in culture for several months and retain their differentiation potential. The findings suggest that the ability to transmit differentiation potentialities is not dependent on the morphological manifestation of these traits. The study highlights the importance of understanding the factors that determine the establishment of myogenic cell lines and the effects of carcinogens on these cells. The results indicate that exposure to carcinogens is not essential for the establishment of myogenic lines. The study concludes that myoblasts maintained in vitro for many months retain their capacity to fuse and differentiate into post-mitotic multinucleated muscle fibers.The study investigates the retention of differentiation potential in myogenic cells during prolonged in vitro cultivation. It was hypothesized that if differentiation depends on preformed informational molecules, continuous multiplication would lead to loss of this potential. Cultures of skeletal muscle cells from newborn rats were studied, showing that myoblasts divide and then fuse into multinucleated muscle fibers. Experiments demonstrated that myogenic cell lines could be maintained for many months without loss of differentiation potential. Cloning experiments showed that the potentiality to differentiate is inherited by virtually all cells. The results indicate that cells maintained in exponential growth can pass on their capacity to fuse and differentiate into muscle fibers. The study also shows that myogenic cells can be maintained in culture for several months and retain their differentiation potential. The findings suggest that the ability to transmit differentiation potentialities is not dependent on the morphological manifestation of these traits. The study highlights the importance of understanding the factors that determine the establishment of myogenic cell lines and the effects of carcinogens on these cells. The results indicate that exposure to carcinogens is not essential for the establishment of myogenic lines. The study concludes that myoblasts maintained in vitro for many months retain their capacity to fuse and differentiate into post-mitotic multinucleated muscle fibers.