This has the effect of narrowing the blastopore. The one exception is the anterior portion of the dorsal blastopore lip. It is now known that the fate of the blastopore in protostomes is extremely variable. The dorsal lip of the blastopore is the mechanical driver of gastrulation. The archenteron will open to the exterior through the blastopore. Gastrulation ends when epiboly of the hypoblasts closes the blastopore. The buccal diverticulum of Balanoglossus has no relationship to blastopore. The Spemann-Mangold organizer is located in the dorsal blastopore lip, where gastrulation movements originate. The open end of the archenteron is called the blastopore. The blastopore will be surrounded by the mesoderm by all sides. Larvae lack a blastopore and do not feed until they are fully developed. C. elegans are a species of protostomes, so the blastopore eventually forms the mouth. The blastopore becomes mouth in annelid larvae, and anus in development of Balanoglossus. Later, the blastopore will be formed and with this, the invagination process is complete. However, in bryozoans the blastopore closes, and a new opening develops to create the mouth.