EDUARD UHLENHUTH 



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to 186 days in Series A, while it is only 60 to 100 days at 25°C. if an 

 unlimited supply of food is allowed the larvae. For this reason it is 

 possible that at high temperature (25°C.), at which regeneration pro- 

 ceeds at a more rapid rate than in lower temperatures, the regenerating 

 larvae were less well supplied with food than the controls, notwith- 

 standing that both received an equal amount, and that this circum- 



TABLE II. 



Regeneration and Metamorphosis in Ambystoma tigrinum. 



Both series kept at 15°C. In Series LVI the fore legs were removed at 26 

 days, from 4.5 to 11 cm. of the tails were removed at 47, 61, 68, 82, 96, 110, 

 124, and 138 days, and the hind legs were removed at 61 days. 



stance caused the delay in metamorphosis in Series E. The experi- 

 ments were apparently unsatisfactory also because they did not 

 warrant a generalization of the conclusion that neoteny could not be 

 brought about by removal of the parts of the body, since the species 

 used might be less prone to neoteny than Triton and Salamandra 

 maculosa. 



Accordingly the experiment was repeated in the spring of 1919 with 

 the larvae of Ambystoma tigrinum, a species frequently found in 

 neotenous condition. With respect to food, a more satisfactory con- 

 dition was established by placing in the jars every day an amount of 

 earthworms greater than was required by the larvae. Two series, a 

 regenerating (LVI) and a control (XLVIII), were kept at 15°C.; 

 both were the offspring of the same female, and each consisted of six 

 animals. They were kept in separate jars and the observations 



