144 The Outline of Science 



sible colours in the common chameleon is greater than in any other 

 animal except the ^Esop prawn. There is a legend of a chameleon 

 which was brown in a brown box, green in a green box, and blue in 

 a blue box, and died when put into one lined with tartan; and there 

 is no doubt that one and the same animal has a wide range of 

 colours. The so-called "chameleon" (Anolis) of North America is 

 so sensitive that a passing cloud makes it change its emerald hue. 

 There is no doubt that a chameleon may make itself more 

 inconspicuous by changing its colour, being affected by the play 

 of light on its eyes. A bright-green hue is often seen on those that 

 are sitting among strongly illumined green leaves. But the colour 

 also changes with the time of day and with the animal's moods. 

 A sudden irritation may bring about a rapid change ; in other cases 

 the transformation comes about very gradually. When the 

 colour-change expresses the chameleon's feelings it might be com- 

 pared to blushing, but that is due to an expansion of the arteries 

 of the face, allowing more blood to get into the capillaries of the 

 under-skin. The case of the chameleon is peculiarly interesting 

 because the animal has two kinds of tactics self-effacement on 

 the one hand and bluffing on the other. There can be little doubt 

 that the power of colour-change sometimes justifies itself by driv- 

 ing off intruders. Dr. Cyril Crossland observed that a chameleon 

 attacked by a fox-terrier "turned round and opened its great pink 

 mouth in the face of the advancing dog, at the same time rapidly 

 changing colour, becoming almost black. This ruse succeeded 

 every time, the dog turning off at once." In natural leafy sur- 

 roundings the startling effect would be much greater a sudden 

 throwing off of the mantle of invisibility and the exposure of a 

 conspicuous black body with a large red mouth. 



4 

 Likeness to Other Things 



Dr. H. O. Forbes tells of a flat spider which presents a strik- 

 ing resemblance to a bird's dropping on a leaf. Years after he 



