METAMORPHOSIS OP" NEOTENOUS AMPHIBIANS 417 



ADDENDUM 



Uhlenhuth's claim that urodeles differ from anurans in that 

 their metamorphosis is independent of iodine and influenced only 

 by the thyroid hormone itself is rendered invalid by the following 

 experiment: The thyroid glands of large axolotls (seven inches 

 total length) were extirpated and the animals kept for five months 

 in the laboratory following the operation, then injected twice 

 with strong doses of tyrosine in which two atoms of iodine had 

 been substituted for two hydrogen atoms of the molecule forming 

 the compound 3-5 diiodotyrosine. The animals metamorphosed 

 within seventeen days following injection. Control thyroidless 

 axolotls injected with equal quantities of pure tyrosine and 

 later with large amounts of 3-5 dibromtyrosine showed no 

 evidences of metamorphosis. 



Further evidence that Uhlenhuth's claim is not valid is fur- 

 nished by Huxley and Hogben who metamorphosed Salamandra 

 and Triton larvae by immersion in dilute solutions of iodine 

 (Proc. Roy. Soc, vol. 93, 1922) ; by Hirschler, who metamor- 

 phosed axolotls and tadpoles by administration of elemental 

 iodine and iodoform (Arch. Entw. Mech., 1922), and lastly by 

 Jensen who metamorphosed axolotls by injections of iodized 

 casein, iodized serum globulin and iodized serum albumen 

 (Compt. Rend. Soc. de Biol., 85, 391-392, 1921). 



BIBLIOGRAPHY 



Adler, Leo 1916 Untersuchungen iiber die Entstehung der Amphibieneotenie. 



Pfliiger's Archiv, Bd. 39. 

 Braus, H. 1906 Vordere Extremitat iind Operculum bei Bombinatorlarven. 



Morph. Jahrbuch, Bd. 35, Heft 4. 

 V. Chauvin, Marie 1875-76. tJber die Verwandlung des mexikanischen Axolotl 



in Amblystoma. Zeitschr. f. wissensch. Zool., Bd. 25, Suppl., und 



Bd. 27. 

 De FiLippi 1861 Sulla larva del Triton alpestris. Arch, per la Zool. e per 



I'Anat. Comp. Geneva (quoted from Gadow). 

 DuMiiRiL, August 1865 Nouvelles observations sur les axolotls nes a la menag- 

 erie. Comp. Rend., T. 61. 

 Emersox, E. T. 1905 General anatomy of Typhlomolge rathbuni. Proc. 



Soc. Nat. History, Boston, vol. 32. 

 Gadow, H. 1909 The Cambridge Natural History, vol. 8. 



