Results of previous research works of the author are discussed in relation to the more recent data. The aim is to present an actual status of the molecular embryology. The transcription is a phenomenon that is acting during the embryonic determination. In some embryonic areas cytoplasmic conditions induce the transcription related to the determination. Amphibian neural inductors are substances of low molecular weight. These inductors are derepressors or induce the formation of the derepressors. In sea urchin development it is possible to put in evidence a transcription corresponding to the animal pole rudiments and a transcription corresponding to the vegetal pole. These transcription processes are induced by the cytoplasm (denatured or stabilized proteins). The substances, that are able to change the determination, act on the cytoplasm. Foreign nucleic acids enter and transform the cells. Competence seems to be a particular kind of determination.