The notochords of three normal, 35-day Mαcαcα mulαttα embryos were examined ultrastructurally. Notochordal cells had numerous polysomes and ribosomes, and some rough endoplasmic reticulum, mitochondria, Golgi complexes, coated vesicles, and secretory granules. A discontinuous basal lamina surrounded the notochord. Intercellular channels and the perinotochordal sheath contained fibrils. It was found that the ultrastructure of the rhesus monkey notochord at stage 17 resembles that of the chick and m