Vol. X] VON GELDERN—SKIN OF ANOLIS CAROLINENSIS 105 



the underlying layer, when passing through this yellow medium, 

 must be so acted upon as to give the yellow. 



The leucophore layer, lying just internal to the oil droplet layer, 

 acts essentially as a reflecting layer. It reflects a large proportion 

 of the light which falls upon it, but it also screens the light to a 

 great extent from the underhv'ing brown melanophores so that 

 pigment granules, when only in the bodies of the melanophores, 

 exert but little influence on the color states of the skin. On the 

 other hand, however, if the primary branches of the melanophores, 

 which pierce this layer, are filled with pigmient, the light which 

 falls on it is reflected as blue light (Fig. loB). Further, cell 

 bodies of the melanophores, lying internal to the leucophore layer, 

 appear blue by reflected light in the scales of the ventral surface 

 of the body in which the yellow oil droplet layer is very scant and 

 in places absent (Fig. 7 B). Evidently then, the leucophore layer 

 in part reflects all the rays of white light and also absorbs all but 

 the blue raj'S from the light passing through it and reflected from 

 the brown pigment within and internal to it. Traversing this 

 leucophore layer are the large branches of the melanophores, con- 

 nective tissue, and finer blood vessels. Partly imbedded in the 

 lower stratum and beneath it are the melanophores. Fig. 17 is an 

 attempt to show in perspective the various layers and their relation 

 to one another. 



The only layer that remains fixed and present in all scales and 

 not subject to variations is the leucophore layer. All the other 

 elements may be either absent, increased, decreased, or subject to 

 marked variations. All of these other elements function in con- 

 junction with the leucophore layer and either by allowing it to 

 be unobscured, partially obscured, or by entirely shutting it off 

 from the light, produce the color phenomena. The appearance of 

 white and pale blue, as found on the ventral aspect of the body or 

 along the mid-dorsal stripe, may be explained as due to the oil 

 droplet layer being either absent or that it has been forced to the 

 edges of the scale. A purely white scale must mean that the mel- 

 anophores are either absent or greatly diminished in nxunber, and 

 very pale blue scales, that their pigment granules must have 

 migrated entirely into the bodies of the cells. This allows the 

 leucophore layer to act alone as a reflecting layer without the in- 

 fluence of any other element. In addition, the stratum corneimi 

 of the scales of the ventral surface is slightly thicker than in other 

 regions, and this greater thickness, with the markedly developed 



