ABSTRACT. A method is described for obtaining large numbers of telotrochs from mass cultures of Vorticella convallaria. These free‐swimming cells contract slightly along the aboral‐oral plane when extracted with Triton X‐100, and thus appear more similar in shape to zooids than unextracted telotrochs. Cytoskeletal structures associated with feeding, such as the infudibulum and the cytopharynx, are visible in cytoskeletal preparations of these non‐feeding telotrochs and thus appear not to be disassembled during telotroch formation. The telotroch to stalked‐zooid transition proceeds rapidly through a set series of morphogenetic stages. After telotroch attachment, the aboral cilia cease beating and are resorbed. Within 7 min the cell is inverted bell‐shaped and the zooid begins feeding. Stalk elongation begins about 15–20 min after attachment, lengthening at the rate of 0.5 μ/min for the first hour and more slowly (0.1 μm/min) after that. Interestingly, these developmental stages are essentially the same as those described for the telotroch to zooid transition in the colonial peritrich Zoothamnium. This evolutionary conservation suggests that the precise sequence and timing of these events are critical for their successful completion. Furthermore, the facts that the telotroch to zooid transition occurs very rapidly, that the feeding structures are maintained throughout the transformation, and that basic cytoskeletal architecture is relatively unchanged is consistent with the hypothesis that the transformation occurs through controlled cytoskeletal rearrangements rather than by changes in gene expression.