84 REPTILES 



of the Squamata, it is evident that their adaptive green and 

 changeable livery has been acquired independently of that of 

 the chamadeon-iguanas (A?w/?s) y which belong to the family 

 Iguanidee. In the case of the Florida chamadeon-iguana 

 {Anolis carolinensis) the extreme ranges of variation in colour 

 extend from dark brown to pea-green ; the former hue (in 

 captive specimens at any rate) being assumed in daylight and 

 the latter at night. The brown condition is induced by the 

 migration of pigment-granules from the centres to the terminal 

 branches and processes of the " melanophores " ; the green 

 state, which is one of rest, being the result of the withdrawal of 

 the granules to the centres of the larger bodies. In three fun- 

 damental points this colour-change differs from that of the 

 chamseleons ; differences which are only natural to expect in 

 phenomena of totally independent origin. When a brown 

 anolis is placed in the dark, it invariably turns green in about 

 five-and-twenty minutes, and when a green one is exposed to 

 the light, it nearly always changes to brown in the short period 

 of about four minutes. Marked differences in the length of time 

 occupied in these changes have been recorded ; and the change 

 from brown to green is often slower at the commencement of 

 an experiment than after it has been continued for some time. 

 This leads to the conclusion that the period of colour-change is 

 shortened by exercise, or practice ; and it has been inferred 

 that a low temperature induces a migration of the pigment- 

 bodies towards the surface of the skin, while a high one is con- 

 ducive towards their withdrawal. This rule appears to be 

 constant for all reptiles subject to a colour-change. On the 

 other hand, light sometimes follows this rule, and sometimes 

 acts in the opposite manner. 



For example, in certain monitors a strong light acts like a 

 high temperature in causing a withdrawal of the pigment-bodies, 

 while a dim light, or darkness, acts in the opposite way. On 

 the other hand, in the African chamseleon and in the chamaileon- 

 iguana strong light acts like low temperature, inducing the mi- 

 gration of the pigment-bodies to the skin, while dim light, or 

 darkness, causes their withdrawal. In other words, while in 

 the first case light and heat act in unison, in the second case 

 their results are antagonistic. 



These lizards are arboreal, hopping from bough to bough 



