EIGHT FIGURESTo most students of the thyroid gland of vertebrates it has seemed for a long time an oddity that diiodotyrosine, one of the precursors of thyroxine, was first identified in the scleroprotein skeleton of corals (Dreclisel, 1896). Even the most recent editions of the chemical handbooks (Hodgman, '52) still list diiodotyrosine as "iodogorgoic acid," the name given to it because it was found in the gorgonid coelenterates. Since the discovery of this substance further work has shown (Ackermann and Burchard, '41 ; Ackermann and Muller, '41 ; Closs, '31 ; Miirner, '07 ; Morner, '08 ; Roche, '52 ; Roche et al., '49 ; Roche et al., '51; Roche and Yagi, '52; JVheeler and Mendel, '21) that sponge and coral skeletons contain, in addition, monoiodotyrosine, mono-, and dibromotyrosine, and even small amounts of thyroxine itself. The recent careful work of Roche ( '52) has established these points, and compares also the characteristic varying proportions of halogenated and other amino acids in different taxonomic groupings of sponges and corallines.The knowledge that iodoproteins and thyrsxinz caa be found in such primitive members of the animal kingdom, and the fact tliat iodine is a common element in marine organisms of various phyletic groups (Cameron, ' l P l 5 ; Closs, '31), 'This study was aided by a contract between Columbia. University and the Office of Naval Research, Department of the Kavy.
