AbstractThe infraciliature and myoneme system ofCampanella umbellariawere revealed using the protargol impregnation technique. The main characteristics of the infraciliature are the peristomial ciliary rows (haplokinety and polykineties), which make four and a half turns around the peristomial disc before plunging into the infundibulum, and the aboral infraciliature, which is made up of the aboral ciliary wreath (trochal band) and the scopula. The myoneme system is composed of: 1) longitudinal fibers, which include 60–84 (mean 72.3) short longitudinal fibers, 40–56 (mean 45.8) medium‐length longitudinal fibers, and numerous long longitudinal fibers; and 2) circular fibers, which include 8–12 (mean 9.3) peristomial ring fibers, linking fibers, support fibers, and peristomial disc fibers. The various fibers inC. umbellariaare interconnected to form a single myoneme system that may act as a cell skeleton as well as providing the mechanism by which the zooid contracts and relaxes. J. Morphol. 261:43–51, 2004. © 2004 Wiley‐Liss, Inc.