GYMNOSTOMACEAE, an order of Ciliate Infusoria (q.v.), characterized by a closed mouth, which only opens to swallow food actively, and body cilia forming a general or partial investment (rarely represented by a girdle of membranellae), but not differentiated in different regions. With the Aspirotrochaceae (q.v.) it formed the Holotricha of Stein.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)