LIGHT AND PIGMENTATION 



87 



Fig. ,j(). — Three Stages in the Dispersion of Pigment in a Mei.anophore 

 OF the Lizard, Taremola (Hogbeii). 



Fic 



TO 59. 



-Pigment Spots in Web of a Frog in Different 

 Conditions (Hogljen). 



Fig. 57. — Dark animal. 





1-^ 





^ ♦ j 







t 



A 



Fig 



5S. — Intermediate 

 condition. 



Fig. 5<). — Pale an 



cells and its streaming towards the surface between them (Schmidt, 

 1920). A compara))le arrangement may be seen in RejDtiles ; thns in 

 the lizard, Anolis, the animal is darkened by the streaming of melanin 

 in the processes of chromatophores to become superficial to an inert 

 whitish layer (v. Geldern, 1921 ; Kleinholz, 1938) (Figs. 62^3), while 

 the proverbial chameleon changes from a dark l)rown to a light green 

 depending on the degree of dispersion of the melanin which lies in front 

 of a sheet of four different kinds of colour-cells. 



The types of 'pi<jment also vary, but the intimate chemical nature 

 of many is unknown. The most primitive and universal pigment is 

 melanin ^ of a dark brown colour ; the cells containing it are usually 

 monochromatic and are termed meJanophores. A second type of 

 pigment — more A'ivid and varied than the dull l^rown of melanin — is 



^ F'or a di-sfussion of the chemical nature of melanin, see p. 118. 



Anolis 



Chameleon 



