536 Observations on the Chameleon. 



Admitting that there are two pigments, a dark and a pale 

 one, each contained in a separate system of cells or follicles, 

 by means of which Mr. Milne-Edwards could make the co- 

 lour of a piece of skin, detached from the body, change from 

 the yellowish grey to the violet red, by pressing the deeper 

 pigment towards the upper surface of the skin, yet these pig- 

 ments themselves must possess the faculty of changing their 

 hues, as no mechanical mixture of two given colours could 

 produce those various tints which the skin of the chameleon 

 exhibits at different times, and among which I have even ob- 

 served the pure primary yellow and red. By the anatomical 

 discoveries of Mr. Milne-Edwards, the solution of the ques- 

 tion has, no doubt, been greatly advanced ; but there are 

 points which must be explained, before we can say that we 

 understand the phenomenon. 



In availing myself of Mr. Milne-Edwards's discoveries, so 

 far as I think they are founded in fact, I am led by my own 

 observations to suppose that the layer of the cutaneous sys- 

 tem which contains the superficial or whitish pigment, (ex- 

 hibiting different tints under different circumstances), always 

 determines the general colour of the animal, when the latter 

 is quite undisturbed, relaxed, or torpid, in consequence of 

 the absence of external or internal irritation ; whereas one or 

 more hues, determined by the rising of the darker (likewise 

 changeable) pigment, begin to develope themselves, and pro- 

 ceed to a limit, determined by the degree and manner in which 

 the chameleon is affected, as soon as the organism and tissue 

 (probably erectile) containing the darker pigment is stimula- 

 ted^ also the superficial tissue containing the pale pigment 

 is depressed by the condition of the integuments. But in all 

 these changes, from the whitest to the darkest hue, heat, light, 

 the quantity of air which the animal inspires, and the differ- 

 ent mental affections, as anger, fear, &c, act a very prominent 

 part* 



To enable the reader to judge better of the view I have 

 taken, I shall enumerate some of the circumstances under 



* I may here observe that although the horny tubercles give rise to viri- 

 descent colours under the direct influence of the sun-beams, yet the pig- 

 ments in general present the true colour which they would show if naked. 

 In one instance, after my specimen had been very dark, in consequence of 

 its vitality having been fully excited, I perceived, on its subsequently be- 

 coming relaxed and whitish, that three or four tubercles remained black. — 

 The skin being cast a month after, I convinced myself that the pigment 

 must have burst, as several follicles were adhering in a dry state to the 

 inner surface of these tubercles, the others being perfectly colourless. 



