Article révisé par les pairs
Résumé : 1. 1. The effects of actinomycin D (an inhibitor of DNA-primed RNA synthesis) and of puromycin (an inhibitor of protein synthesis) have been studied in two different biological systems: amphibian eggs and the unicellular alga Acetabularia mediterranea. 2. 2. Actinomycin D, even after microinjection, does not stop cleavage in amphibian eggs; it interferes with gastrulation and, especially, nervous system formation. 3. 3. Puromycin also inhibits nervous system differentiation in amphibian eggs. 4. 4. Anucleate fragments of Acetabularia, in contrast to nucleate ones, can form caps in the presence of actinomycin D. Later growth of these caps is, however, inhibited. 5. 5. Puromycin inhibits growth and morphogenesis in both nucleate and anucleate halves of Acetabularia; the effect is reversible in the former, but abnormalities of regeneration are frequent under these conditions. 6. 6. The results are discussed in the context of modern theories in molecular biology (intervention of messenger RNA's, formation of polysomes, possible role of cytoplasmic DNA, etc.). © 1964.