XI THE COLOURS OF AMPHIBIANS 235 



The effect of light on the developing larvae was 

 also tested, and it was found that light has but little 

 effect, though on the whole the larvse are darker in 

 light than in darkness. This is interesting because 

 the same thing has been noticed in tadpoles of the 

 frog, which become pale and transparent in darkness, 

 while adult frogs, many fishes, reptiles, etc., become 

 pale in strong light. Thus at least in the frog the 

 larva and the adult react differently to the stimulus 

 of light. 



As an interesting corhmentary upon these obser- 

 vations of Fischel's, we may note that Bedriaga in 

 describing the larvae of Molge aspersa, remarks that 

 while the colour is usually an olive -brown with 

 yellowish spots, larvae taken from deep water are 

 much darker in tint, and the yellow spots are reduced 

 both in size and intensity. On the other hand, 

 larvae from sunny shallow situations are pale in 

 colour and very distinctly spotted with yellow. As 

 Fischel found that light as a whole tended to darken 

 the colours, we must suppose that in this case it is 

 the temperature of the water in the two situations 

 which is important in affecting coloration. 



Similarly, Karl Knauthe found that adult Am- 

 phibians {Bufo variabilis and B. vulgaris, Pelobates 

 fuscus, and others) turned dark, often gray or black, 

 when exposed to the influence of intense cold. It 

 would appear from this observation that the larvae 

 and adults react similarly to variations in temperature. 



