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



the scales are now viewed externally by reflected light, they no 

 longer have the green appearance, but appear deep blue just as do 

 the previously described scales viewed from the internal surface 

 by reflected light (Fig. 6 C). The melanophores, however, are 

 blue and indistinct, indicating, as was later found, that a semi- 

 transparent reflecting layer exists between them and the surface 

 and that this layer is evidently not affected by ether or alcohol. 



The explanation for the green color is now quite apparent, for 

 blue rays are reflected and these in passing through a clear yellow 

 medium present to the eye the green color. 



The semi-transparent reflecting layer lying between the melano- 

 phores and the external surface reflects bluish-white light as is 

 evident in those scales in which little or no coloring matter exists 

 and in which the melanophores are sufficiently separated so as not 

 to influence the reflected light to any extent. This is true of the 

 scales on the ventral aspect of the body, in individual lateral 

 scales, and the white ones often found along the mid-dorsal line. 



Histology 



That the tissue relationship of the skin might be more carefully 

 analyzed with the purpose of attempting an explanation for the 

 changes of color, a nimiber of lizards in various color states were 

 killed and segments of the body fixed in different fluids. It was 

 found that segments placed for about six weeks in a fluid consisting 

 of 3-5% potassium bichromate loo parts, formalin 4 parts, and 

 glacial acetic acid 5 parts, gave the best results. Tissue fixed in 

 this fluid maintained the cellular relationship and the osseous 

 structures were sufficiently decalcified so that entire sections of 

 the body could be made. 



Formalin was found to act too slowly with segments of the body. 

 Lizards in the green state became brown during its action. It was 

 possible, however, to overcome this difficulty by injecting formalin 

 quickly with a hypodermic needle under the green skin, thus 

 obtaining almost immediate contact of the fluid with the entire 

 internal surface of the skin. This method has a distinct advantage 

 in that the animals may be studied on the table for a considerable 

 length of time after fixation and the color state carefully recorded. 

 Unfortunately, however, after a longer time the green color be- 

 comes changed to a slaty gray after the use of formalin, due most 

 probably to a change in the yellow coloring matter. Removing 

 the skin and washing it in water soon after fixing prevents this 



