Etude histologique de la régénération pharyngienne de Syllis gracilis Grube (Annélide, Polychète)

During anterior regeneration of Syllis gracilis Grube (Annelida, Polychaeta), the pharynx (pharyngeal sheath, proboscis, proventricle, and ventricle) completely regenerates. Most of the regenerated pharynx (pharyngeal sheath, proboscis, and proventricle) proceeds from direct transformation of the stomodeal invagination. On the other hand, the ventricle seems to come from both the posterior end of the regenerated proventricle (anterior part of the ventricle) and the intestine of the stump (posterior part of the ventricle corresponding to the ventricular coeca).Tile differentiation of the pharynx is precocious and mainly appears in a particular disposition, and a typical evolution of the cells of the mesodermal sheath surrounding the stomodeal invagination. Starting from the 11th day after amputation, the proventricle differs from the presumptive proboscis by a thick mesodermal sheath which forms the radial muscle cells, the transverse diaphragms, and the peritoneal epithelium. On the other hand, the differ...