228 COLOUR IN NATURE chap. 



uniformly distributed in the larvae than in the adults, 

 and that development is accompanied by a re- 

 distribution of pigment as well as by changes in 

 amount. It is interesting to note that in Am- 

 phibians as in Fishes colour-changes, whether natural 

 or artificially produced, are not confined to the skin 

 but occur also in internal structures, e.g. the peri- 

 toneum. 



In studying the pigmentation of larvae we may 

 take first the case of the spotted salamander {Sala- 

 mandra maculatd), where the coloration has been 

 described in detail by Fischel. This salamander is 

 often kept in confinement, and the vivid black and 

 yellow colouring of the adult is very familiar. The 

 larvae under normal conditions when nearly full- 

 grown are almost entirely black, the black pigment 

 occurring in spots on a somewhat lighter ground. A 

 histological examination shows that the colour is due 

 to the action of four factors, which are as follows : — 



(i) Pigment granules lying in the cells of the 

 epidermis. 



(2) Branched pigment cells lying between the 

 epidermal cells, sending their processes into the 

 intercellular spaces. 



(3) Similar branched pigment cells lying beneath 

 the epidermis in the true skin or dermis. 



(4) Pale yellow cells similar in character and 

 position to (3) but in the normal condition largely 

 concealed by these. 



In the first three cases, the pigment is melanin of 

 dark brown or black colour, in the fourth it is yellow 

 lipochrome. The pigment cells of the dermis — 

 black and yellow — are by far the most important 



