XI THE COLOURS OF AMPHIBIANS 229 



factors in coloration, the epidermic pigment having 

 relatively little effect. In the larva, the dermis over 

 its whole area contains both black and yellow cells, 

 but the latter are more abundant at certain regions, 

 corresponding to the future yellow spots of the adult. 

 The peritoneum contains also both yellow and black 

 cells, while in the adult there is no trace of yellow 

 cells in it. 



Fischel's observations on the coloration were made 

 in connection with some experiments on artificially 

 produced colour -change, and he did not therefore 

 carry them beyond this point. Before proceeding, 

 however, to consider the theoretical bearing of the 

 facts given above, we may supplement them by some 

 notes made by Dr. Bedriaga on the development of 

 colour in the larvae of newts. Bedriaga did not 

 investigate the histology of his specimens, but in 

 view of the similarity of colour, we are probably 

 justified in applying Fischel's statements throughout. 



We may take the case of Molge montana, which 

 is described in some detail, as typical of one set. In 

 this form, larvse 10-15 mm. in length are uniformly 

 yellow beneath, and yellowish-white with black spots 

 above. Larvae 20-25 mm. in length show these 

 black spots spreading over the light ground, especially 

 on the upper surface. From 25 up to 40 mm. the 

 larvae show a gradual increase of the black pigment 

 which now becomes the ground colour, the light pig- 

 ment appearing in the shape of small spots, but 

 forming also a median yellow stripe. Larvae of 40- 

 45 mm. length appear when taken from deep water 

 to be perfectly black, but if placed in shallow vessels 

 they become much lighter, and then exhibit very 



