In Stentor coeruleus, AZM shedding leads to formation of a primordium in the ciliary cortex, accompanied by modification in macronuclear morphology.

The DNA and RNA syntheses are studied by autoradiography on synchronised cells of exponentially growing cultures (cellular cycle 18 h).

Dividing cells show a short G₁ phase, DNA synthesis begins 4 h. after division with a maximum at stage 3-4 of the morphogenetic period. RNA synthesis is uninterrupted.

Regenerating cells show some parallelism with dividing ones : DNA synthesis is maximum at stage 3, RNA synthesis maximum at stage 4.

The synthesis of nucleic acids is coordinated with regeneration stages.

The use of specific inhibitors of DNA and RNA (nalidixic acid, mitomycin, hydroxyurea, actinomycin) shows the necessity of the nucleic acids in the morphogenetic process. Several hypotheses about the role of these nucleic acids are discussed.