THE OCCURRENCE, DISTRIBUTION AND ATTACHMENT OF THE PEDUNCULATE BARNACLE OCTOLASMIS MÜLLERI (COKER) ON THE GILLS OF CRABS, PARTICULARLY THE BLUE CRAB. CALLINECTES SAPIDUS RATHBUN.

1. O. mülleri was present on the gills of most crab species in Beaufort Inlet but not on C. sapidus further upriver indicating that salinity is probably a factor controlling the incidence of the barnacle. 2. The distribution of the barnacle on the individual gills of C. sapidus has been analyzed and the factors affecting this distribution discussed. The main factors are the cleaning action of the epipodites and the respiratory flow of the crab. 3. The barnacle settlement stage larva (cyprid) attaches to blue crab gills a short distance in from the gill margin. The orientation of the larva at settlement is a response to the respiratory flow of the crab resulting in the cirral net of the young barnacle facing into the current. 4. The cement apparatus and internal stalk structures of O. mülleri and Lepas anatifera are compared.