36 



Experiments on Amphibian Metamorphosis and Pigment Responses 

 in Relation to Internal Secretions. 



By J ulian S. Huxley (New College, Oxford) and Lancelot T. Hogben 

 (Imperial College of Science, London). 



(Communicated by Prof. E. W. MacBride, F.R.S. Received July 26, 1921.) 



CONTENTS. 



PAQE 



1. Metamorphosis of the Axolotl by Thyroid Administration 36 



2. Acceleration of Metamorphosis by Iodine with Triton and Salamandra Larvae 42 



3. Negative Effects of Administration of other Ductless Glands and Iodine on 



Metamorphosis in Axolotl 44 



4. Effect of Thyroid Feeding on Necturus 46 



5. Pigmental Reactions of Axolotls to Adrenal and Pituitary Hormones 48 



6. The Pineal Pigment Cycle in Frog Tadpoles 51 



Summary 52 



The problem of metamorphosis in Amphibia attracts attention from many 

 points of view. These organisms have, one may say, acquired interest as 

 being indicators for the action of certain internal secretions ; the underlying 

 mechanism of metamorphosis is still imperfectly understood ; and the general 

 biological problems involved, especially with respect to the neotenous and 

 perennibranchiate forms, are remarkably fascinating. The experiments here 

 recorded were undertaken with a view to elucidating these issues more fully, 

 and in the course of them data relevant to the pigmental responses of Amphibian 

 larvte also emerged. For various reasons it was deemed desirable to publish 

 an account of the observations so far completed. Acknowledgment is made to 

 Mr. D. F. Leney of New College for assisting in the care of animals, to the 

 Royal Society and the Trustees of the Dixon Fund for grants in aid of the 

 expenses incurred by the authors respectively, and to Prof. E. W. MacBride, 

 F.R.S., for his kindness in reading the MS. 



1. Metamorphosis of the Axolotl by Thyroid Administration. 



(a) When a note (Huxley, ' Nature,' 1920) on the metamorphosis of medium - 

 sized but immature Axolotls by means of thyroid feeding was published by 

 one of the authors a year ago, and confirmed a few months later (Hogben, 

 ' P.Z.S.,' 1920), our attention had not been called to Jensen's work (1916). 

 Since this appears to be little known and is not readily accessible to English- 

 speaking workers, it is proposed to give a short re'svme' of some of his most 

 important findings. 



