Various treatments which induce precocious fixation or inhibit attachment of Bugula and Amaroecium larvae are reviewed. Heilbrunn\u27s general theory of stimulation and anesthesia is thought to provide a fairly suitable explanation for the artificial induction or inhibition of metamorphosis of Bugula larvae, but the agents causing induced metamorphosis resemble those which affect cell division more than those which affect muscle contraction, a necessary correlate of the hypothesis. The hypothesis applied to Bugula larvae does not seem to offer a suitable explanation for induced metamorphosis in some ascidian tadpoles
