DISCUS

(Lat.), n. m. Di2sk'u3s(u4s). See Disc. D. brach i ferns. See Brachiferous DISC. D. central is. See Umbrella DISC. D. cerebelli. In certain fishes, the inferior surface of the cerebellum, which forms the roof of the fourth ventricle. [L, 14.] D. epigynus. See Epigynous DISC. D. genu. See PATELLA. D. lei it i form is. See Lenticular NUCLEUS. D. oophorus. See D. pro liger us.'D. options. See Optic DISC. D. pro liger us [von Baer]. Fr., disque proligere, cicatricule. Ger., Hahnentritt, Narbe, Hauptkeim [His], Keimschicht, Keimscheibe, Keimhiigel. It., disco proligero. Sp., disco prolifero. Syn.: stratum proligerum. In oviparous animals, a granular disc immediately beneath the vitelline membrane, marking the beginning of the formation of the blastoderm. Viewed cro wise, it has the appearance of an umbilicus, whence it has also been termed the cicatricula. From the disc it projects inward in the form of a cone-like granular accumulation, the cumulus pro liger us, encroaching on the vitellus. [A, 45.] D. uinbralis. See Umbrella DISC. D. vitellin us. See D. pro liger us. [s. 593]