50 THE SENSES OF ANIMALS 



apex of the cone the comparatively small eye is visible. These 

 eye housings are capable of independent movement so that 

 the chameleon is able to direct one eye forwards and the 

 other eye backwards ; or one eye upwards and the other 

 downwards, with intermediate positions as well. This curious 

 adaptation is said by some to enable the chameleon to per- 

 ceive an insect in front of it with one eye, while keeping a 

 look out for possible enemies behind it with the other eye. 

 This has always seemed unlikely to me because chameleons 

 are so slow-moving by comparison with other lizards that 

 they would be unable to escape from a marauding snake, for 

 example, if the backward-looking eye did spot the poten- 

 tial foe. 



It is more reasonable to consider that this independent 

 movement of the eyes allows the chameleon a very wide 

 range of vision when seeking food, and this all-round sight, 

 coupled with the long, sticky and swiftly operated tongue, 

 compensates for the slowness of locomotion. Chameleons 

 stalk their prey, they do not catch it by swift darts and 

 rushes as do so many other lizards. 



As some students may well wish to have a chameleon for 

 observation, it must be pointed out that they are not the 

 easiest of reptiles to keep in health. The real reason for this 

 is not thoroughly understood even by zoo authorities; but 

 one reason for the failure of most novices to keep chameleons 

 alive is because they are not able to heat the vivarium effi- 

 ciently. A temperature of 70° F. is desirable so long as plenty 

 of foliage is provided and kept alive ; some of the heat should 

 come from a lamp — even a reading-lamp will do — so that 

 the chameleons may bask at will. 



Another reason for failure is connected with the drinking 

 habits of chameleons. It is no use placing a little dish of 

 water in the vivarium and hoping for the best. Personally 

 I have never known a chameleon drink from such. In nature 

 they drink by lapping with their tongues the dew on leaves, 

 or raindrops. In captivity the foliage in the vivarium should 

 be sprayed with a fine spray at least every other day. Ventila- 

 tion must also be good otherwise an over-damp tank will lead 

 to rotting vegetation which is not, for some reason, good for 

 chameleons. 



