570 CHAMAELEONTES CHAP. 



By rapidly filling the apparatus with blood, and by the action of 

 certain hyoid muscles, the spring is, so to speak, released, and the 

 momentum gained by the thick and heavy club-shaped tongue proper 

 projects it far out of the mouth. The sticky end of the club shapes 

 itself into an upper and a lower flap, which partly envelop the 

 prey, and the elastic bands of the far-stretched stalk withdraw the 

 whole. The detailed working of this ingenious shooting apparatus 

 is not easy to follow. An ordinary full-grown Chameleon can 

 shoot a fly at the distance of 7 or 8 inches. The whole 

 performance is very quick, lasting less than one second. When 

 the desired object is very near, only 2 or 3 inches off, the 

 Chameleon has a certain difficulty in shooting its prey. The 

 tongue is at first put out slowly, tentatively, the following jerk 

 is feeble, and it seems as if the apparatus refuses to work unless 

 it is allowed to shoot out with full force. 



Another remarkable and quite proverbial feature of Chameleons 

 is their changing of colour. This is by no means restricted to 

 Chameleons, which indeed are rivalled in this respect by various 

 other lizards, for instance by the Indian Agamoid Calotes and by 

 the American Ameiva. 



The microscopical structure and mechanism of the colour- 

 changing apparatus is, in Chamaeleon vulgaris, as follows : 



The epidermis is colourless, and the Malpighiari layer is not 

 particularly modified except that in it are imbedded some iri- 

 descent cells, with very minute wavy striation on their surface. 

 The cutis contains in its leathery tissue a great number of small 

 and closely packed cells, filled with strongly refractive granules, 

 chiefly guanine-crystals. These cause the white colour by diffuse 

 reflection of direct light, -The cells nearer the surface are charged 

 with oil-drops and appear yellow. Large chromatophores are 

 imbedded in the white granular mass, most of them with blackish- 

 brown, others with reddish pigment, the granules of which are 

 shifted up and down, towards and away from the surface of the 

 cutis, in ramified branches of the chromatophores. When these 

 branches are contracted the pigment is conveyed back into the 

 bulbous basal portion of the chromatophores and the skin appears 

 yellow or white. When all the pigment is shifted towards the 

 surface of the cutis, the animal looks dark, sometimes black. In 

 intermediate conditions the light is changed into green by 

 diffraction through the yellowish upper strata and by the finely 



