106 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



keel of the scale found here, no doubt results in more light being 

 reflected from the outer surface of the scale and thus a whiter 

 appearance. It seems probable that by a vaso-dilatation of the 

 superficial capillaries a pink color may be imparted to the white 

 scales. Further, in addition to the blood capillaries, red pigment 

 is manifestly present in the subcutaneous connective tissue of the 

 throat-fan. 



If, in the white scales, melanophores are present and send out 

 pigment into the primary and larger branches, the light, which is 

 now acted upon by the leucophore layer, is returned as blue. 

 Decidedly blue scales are rare except in isolated scales on the 

 lateral aspect of the body. Along the mid-dorsal stripe and on 

 the ventral aspect, melanophores are too few in number to influence 

 the color beyond a pale blue. I injected brown pigment (potassium 

 bichromate solution) into the skin of the belly, and a blue color was 

 readily produced. Higgins' brown ink furnishes the same result 

 in the same way. 



The yellow or orange appearance may be readily explained by 

 the presence of the yellow oil droplet layer through which light 

 from the leucophore layer must be transmitted. The melano- 

 phores, in the case of the yellow skin, must contain the pigment 

 in their bodies, and the branches must be free of pigment. The 

 degree of yellow color depends on the amount of oil droplets, the 

 straw-yellow color being associated with a lesser amount than 

 the deep yellow. Pale yellow is often present on the ventral 

 aspect of some lizards due to the presence of a small amount of 

 this substance. 



The emerald green is brought about by the migration of pig- 

 ment into the primary and larger branches of the melanophores. 

 Now the light which is reflected from the leucophore layer, due to 

 the presence of pigment granules, is blue, and this blue, in pass- 

 ing through the yellow oil droplet layer, mixes with yellow rays 

 given by this layer and appears at the surface as green. By 

 further distal migration of the pigment granules, light from the 

 leucophore layer assumes a deeper blue which in turn produces 

 the bluish-green color of the skin. 



By a still more distal migration of the pigment a muddy, 

 greenish gray appears which, as the migration proceeds, becomes 

 brownish gray, then light brown and, lastly, a deep mahogany 

 brown is produced, which indicates that distal migration has pro- 

 ceeded till the granules have accumulated immediately beneath 



