Metamorphosis in the Colorado Axolotl 51 



Abstracts of Communications, Pacific Coast Branch 

 Thirty-fourth meeting. 

 Berkeley, California, October 15, 1922 

 21 (1981) 



Retardation of metamorphosis in the Colorado axolotl by the 

 intraperitoneal injection of fresh bovine hypophyseal 

 anterior lobe substance 1 . 



By PHILIP E. SMITH and IRENE B. SMITH 



[From the Anatomical Laboratory, University of California, 

 Berkeley, California] 



As is well known, the axolotl in its native habitat may retain 

 its larval condition for long periods, even becoming sexually 

 mature (neotonous). When treated with thyroid, when placed 

 in unfavorable conditions or when transported to a lower and 

 warmer region it rather promptly metamorphoses. This delicate 

 balance obtaining in the internal secretory glands (the thyroid 

 and hypophysis here being of especial interest) of this form 

 would appear to make it especially useful in the experimental 

 modification of the activities of these glands. Since the experi- 

 mental transplantation of the anuran anterior hypophysis into 

 the hypophysectomized tadpole (Allen) and into the normal 

 tadpole (Swingle) and the intraperitoneal injection of bovine 

 anterior hypophyseal substance into the pituitaryless tadpole 

 (Smith) appear to stimulate the thyroid, thus hastening or in- 

 ducing metamorphosis, it would seem that the injection of this 

 substance might be expected to accelerate metamorphosis in the 

 axolotl. The opposite reaction, however, is evoked, the larval 

 condition being decisively prolonged. The experimental injection 

 of fresh bovine anterior lobe hypophyseal substance, intraperi- 

 toneally, into the Colorado axolotl during the months of May 

 to September af the present year has resulted In a definite re- 

 tardation in the metamorphosis of this form. Anterior lobe 

 substance appears here to have given a "paradoxical" reaction 

 and the usual effect of thyroid activity (which most investigators 



1 Aided by a grant from the Elizabeth Thompson Science Fund. 



