ANIMAL ORGANIZATION. 103 



trating through a more superficial layer of yellow, 

 white, or grey pigment, which lies immediately 

 underneath the epidermis, in the situation usually 

 occupied by the corpus mucosum. In the ordinary 

 state of the Chameleon, the colour of the skin is 

 determined by this yellow pigment; the whole of 

 the dark pigment being collected in the subcuta- 

 neous follicles, which are concealed underneath 

 the true skin. When, on the other hand, these 

 follicles contract, or are compressed by the action 

 of the skin or neighbouring muscles, the dark pig- 

 ment they contain is propelled into the tubes and 

 their ramifications, and becomes visible by its in- 

 termixture with the yellow and grey pigment, 

 which, if the former be very abundant, it may over- 

 power and wholly obliterate. The apparent colour 

 of the skin, therefore, is determined by the propor- 

 tion in which the two pigments become visible, and 

 the degree in which the one predominates over the 

 other.* 



Connected with the skin, and more particularly 

 with the cuticle, are structures of very various 

 forms, intended for giving additional protection, 

 occasionally contributing their aid in progressive 

 motion, and sometimes fashioned into weapons of 

 oflence. In this class should be included all the 

 varieties of hair, such as wool, fur, feathers, bristles, 

 quills, and spines, as well as the more ordinary 

 kinds of hair. All these resemble the cuticle in 

 their chemical composition, differing only in their 

 degrees of hardness and condensation. Horn is 

 formed of the same material as hair ; as are also 



* Ann. Sc. Nat. serie 2. i. 46. 



