536 METAMORPHOSIS IN AMPHIBIANS 



wise they were kept under exactly like conditions. The eggs from 

 which they hatched in the laboratory were collected in Syosset, Long 

 Island, in the spring of 1917; they were all taken from one single egg 

 mass and were consequently laid by the same female. Soon after 

 hatching the larvjE of both sets were fed on worms, which were used 

 as food throughout the whole experiment. Each set consisted of six 

 specimens; five of these metamorphosed in Series 5 and four in Series 

 U . In Series S, metamorphosis took place 11 weeks and 6 days after 

 hatching, in Z7, 22 weeks and 2 days after hatching. 



In both series the color of the larva; before metamorphosis was an 

 even greenish black. 



In Series 5 numerous yellowish spots of small size became visible 

 all over the back as soon as the larvae had shed the skin (Fig. 5). 

 In Series U the larval color was retained after metamorphosis and no 

 spots appeared; metamorphosed animals with a larval coloration 

 resulted (Fig. 6). 



In Series S the yellow spots soon began to increase considerably in 

 size; in Series U no yellowish spots appeared before the 2nd week 

 after metamorphosis, when a small number of tiny sepia colored 

 specks made their appearance. 



In Series S the yellowish spots had increased so much in size several 

 weeks after metamorphosis that they became confluent here and there 

 forming yellow blotches; no further changes took place in Series U. 

 Fig. 7 shows an animal of Series 5' 13 weeks and 2 days after meta- 

 morphosis; the spots have fused to form blotches and bands of yel- 

 lowish color. Fig. 8 shows an animal of Series U , 22 weeks and 3 

 days after metamorphosis; the spots are still small and few in number. 



The final coloration of the adults is shown in Figs. 9 and 10. In 

 Fig. 9 an animal of Series S is shown 3i weeks and 2 days after meta- 

 morphosis; very little of the black background is left, most of it being 

 filled in by the large yellowish bands; in the animals kept at low tem- 

 perature just the opposite occurs, as is shown in Fig. 10, 50 weeks 

 and 5 days after metamorphosis. The number and size of the 

 yellowish spots have increased only slightly. 



These experiments show that the occurrence of banded and spotted 

 individuals in Amhystoma tigrinum is not due to the existence of two 

 different races, since in our experiments all animals were derived 



