Three morphogenetic waves in early development of Physa acuta (Gastropoda, Pulmonata)

Evidence is presented that there are three morphogenetic waves in early development of Physa acuta: a) around 24-cell stage, b) at early gastrula, and c) at early trochophore, using a proflavin biological test. These morphogenetic maxima fit very well with three transcriptional maxima. Furthermore, it is shown that proflavin inhibits almost completely the RNA synthesis.