SIGHT — FIELDWORK AND EXPERIMENTS 49 



feed from the hand, but crocodiles — almost without excep- 

 tion — are more vicious in character and seldom become as 

 docile as alligators. I do not know why this is and I have 

 never come across any explanation in the course of my read- 

 ing. Both crocodiles and alligators can be trained to take 

 dead fish or meat according to species, but this kind of food 

 never seems to produce such healthy specimens as those 

 which can be fed on live fish, frogs, snails and so on. This is 

 curious when one considers that "high" meat is relished by 

 some kinds of crocodiles and alligators — perhaps those of us 

 who have kept such reptiles as pets or as subjects for class 

 observation are averse to allowing food to become putrid 

 before offering it ! 



Both crocodiles and alligators have good nocturnal vision, 

 though their eyesight is quite acute in anything but really 

 bright sunlight. 



In the lizards we meet the reptiles which are endowed 

 with the best sight of all. There are so many species of lizards 

 which can be kept in captivity that it is simple to carry out 

 experiments to prove the great acuity and accommodation 

 which their eyes are capable of Our own Common Lizard, 

 Sand Lizard and Slow Worm will demonstrate this soon after 

 capture, while among the foreign species the Wall Lizards, 

 Eyed Lizards, and Green Lizards of Europe are equally satis- 

 factory and can all be kept in vivaria provided that the 

 temperature is not less than 60° F. 



The Geckos are worth observing because they feed almost 

 entirely at night or at dusk, and if fed with grasshoppers, 

 moths, craneflies, etc., their bodily agility and keen sight can 

 be observed and studied so long as the room in which they 

 are kept is dimly lighted. It is my experience that Geckos will 

 feed more readily in subdued Hght, although those who have 

 lived in hot climates know that the Geckos, which so often 

 take up residence in houses and bungalows, will display their 

 powers in well-lit rooms where moths, beetles, and other 

 flying insects are drawn to the source of light. 



Special mention must be made of the chameleons, not just 

 because they have the same sharp sight as other lizards, but 

 because of the unique structure of their eyes. The eyeball is 

 "housed" in a cone-shaped turret-like structure; and in the 



