Abstract
The ultrastructure of the compound eye of an ascothoracid larva — the only known occurrence of compound eyes in the Ascothoracida — is described. The ommatidia of apposition type consist of a crystalline cone composed of three cells and up to six retinular cells. Poor fixation of the scarce material allows no safe judgement about the number of retinular cells and the nature of two distal cells surrounding the crystalline cones. The structure of these compound eyes most closely resembles the cirriped compound eye.