Abstract <p>The use of molecular phylogenetic methods has caused a profound rearrangement of the system and phylogeny of the triploblastic Bilateria (=Triploblastica). Nevertheless, in most phylogenetic trees, two main clades remain, coinciding with Protostomia and Deuterostomia, established by K. Grobben (1908) more than 100 years ago. For both clades of Triploblastica, amphystomy is the primary way of forming a through gut. However, the analysis shows that only the origin of the mouth and anus does not allow us to distinguish between the two main clades. All the groups that were referred to Grobben’s Protostomia are characterized by an ectodermal pharynx, therefore this clade would be more correctly called Ectopharyngeata. Based on the modification of the pharyngeal cuticle, many ectopharyngeates develop various structures designed to grind food. The groups attributed by Grobben to Deuterostomia have an endodermal pharynx, therefore it would be more correct to call this clade Endopharyngeata. The synapomorphy of Endopharyngeata is the development of gill slits in the walls of the endodermal pharynx and the division of the pharynx into two zones: the dorsal branchial zone and the ventral digestive zone. During the evolution of the chordates, the sides of the body were inverted. As a result, the part of the digestive tube that is homologous to the hemichordate digestive zone of the pharynx became the dorsal notochord and the branchial zone of the pharynx turned out to be ventral. Thus, the division of Triploblastica into two clades entirely retains its significance in modern biology, although it is based on a different set of morphological features than that considered by Grobben.</p>