Macrostomorpha taxonomy and phylogeny

"The large , ventrally disposed mouth, coupled with the highly distensible enteric sac, enables the animal to ingest others almost as large as itself. When in such a gastronomic dilemma, the animal lies quietly, while the large irregular bulk of food is reduced to a convenient size by enzymic action."

From Ferguson, 1939. A monograph of the genus Macrostomum O. Schmidt 1848. Part I, p14