During the third week there appears, immediately behind the ventral ends of the two halves of the mandibular arch, a rounded swelling named the tuberculum impar, which was described by His as undergoing enlargement to form the buccal part of the tongue. More recent researches, however, show that this part of the tongue is mainly, if not entirely, developed from a pair of lateral swellings (or distal tongue bud) which rise from the inner surface of the mandibular arch and meet in the middle line. [ http://en.wikipedia.org/wiki/Lateral_lingual_swelling ]