The Post-Larval Stage of Arenicola marina

Abstract

By “post-larval stage” I wish to indicate that stage in the developmental history of Arenicola at which the full adult number of somites has appeared, and the body is already distinguishable into (a) an anterior chætigerous region, and (b) a posterior achætous region or tail, but in which the gills are not yet completely formed or have not yet even made their appearance.