By the first years of the 19th century, the term 'mate', without the prefix master's, was used for passed midshipmen, to distinguish them from master's mates who had not served as midshipmen. In 1824, the rating of master's assistant replaced master's mate, and mate continued to be used unofficially by passed midshipmen. These changes helped eliminate the confusion caused by the mingling of midshipmen in the navigator's branch. In 1838 a Royal Commission, presided over by the Duke of Wellington, recommended the institution of the rank of mate as an official step between midshipman and lieutenant. In 1861 mate was abolished in favor of sub-lieutenant.