Abstract
It has been shown that the early development of the monogenean Calicotyle kröyeri takes place in the rectal gland of its hosts (various species of Raja). Adult parasites were found in the rectal gland as well as in the cloaca. The invasion route followed to the rectal gland remains unknown, in spite of a search for post-larvae in scrapings from the cloacal lining, rectal lining and ventral skin near the cloacal opening and in blood vessels leading to and from the rectal gland. The growth of the hamuli is described.