SPONTANEOUS METAMORPHOSIS OF THE 

 AMERICAN AXOLOTL 



PEOFESSOR W. W. SAVINGLE 

 OsBORN Zoological Laboratory, Yale University 



The following experiments on axolotl neoteny and meta- 

 morphosis are published, not because of the conclusive 

 nature of the results obtained, but the reverse— because 

 of their inconclusiveness. A record of the work seems 

 warranted in order that other investigators of this prob- 

 lem may be spared considerable expense, time and effort 

 due to unsuitability of the material for experimentation. 



The latter part of April, 1922, one hundred and nine 

 axolotl larvae of Amblystoma tigrinum were received 

 from Albuquerque, New Mexico. These animals were 

 obtained through the courtesy of Mr. J. N. Griadding. 

 They varied in length from four inches to fourteen 

 inches, though the average total length was about seven 

 inches. One animal measured fourteen inches from 

 snout to tail tip, another measured eleven inches. They 

 were the largest individuals of the lot. The animals were 

 in excellent condition on arrival and none showed any 

 indications of metamorphosis. 



ExPEKiMENT 1. Autoplastic Thyroid Transplantation' 

 May 5, 1922, the thyroids of seven axolotls, seven inches 

 in length, were removed under chloretone anesthesia and 

 each gland transplanted intraperitoneally into the same 

 individual from which it was taken. The idea was that 

 the acquisition of a new blood and nerve supply by the 

 gland in its new environment might permit the release 

 of the accumulated secretion and so metamorphose the 

 animal. It was shown by the writer ( '21) that the thy- 

 roid glands of axolotls are highly active metamorphosis- 

 inducing agents providing the hormone escapes into the 

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