XI THE COLOURS OF AMPHIBIANS 233 



the purity and brilliancy of the colouring, as well 

 as to give rise to markings. An inquiry into the 

 causation of the process would be of great interest. 



Colour Variation in Larv^ 



As we have already seen, the larvae of Amphibians 

 are very sensitive to environmental influences, their 

 colour changing according to the conditions under 

 which they are found. This fact was noticed both 

 by Fischel and Bedriaga, and the former made some 

 extensive experiments on the subject. He and one 

 of his colleagues obtained a number of larvae of 

 Salamandra maculata. Half were put in a fish- 

 hatching apparatus, and the other half in standing 

 water in a dish. The former displayed the ordinary 

 type of coloration, the latter were distinctly lighter 

 without displaying any other abnormality. The 

 ground colour was a light yellowish-white, and the 

 ordinary black spots were only represented by slight 

 traces of dark pigment, occurring especially at the 

 posterior end of the body. As well as displaying 

 little pigment, the larvae are said to have had a 

 peculiar glassy and transparent appearance. The 

 larvae were not all uniform, but showed considerable 

 variation, those in the standing water were, however, 

 all much lighter than those in the running water. 



On making a histological examination of the skin 

 of the pale larvae, it was found that the cells of the 

 epidermis contained a much smaller amount of 

 pigment than usual, while the branched pigment cells 

 of this layer and of the underlying dermis were 

 represented by dark-coloured oval or rounded bodies. 



