286 Animal Life and Intelligence. 



Concerning the sense of sight in reptiles and in 

 amphibians, little need here be said. At near distances 

 some of them undoubtedly have great accuracy of vision. 

 This is, perhaps, best seen in the chamseleon. In this 

 curious animal the eyes are conical, and each moves freely, 

 independently of the other. The eyelids encase the organ, 

 except for a minute opening, looking like a small ink-spot 

 at the blunted apex of the cone. The animal catches the 

 insects on which it feeds by darting on to them its long 

 elastic tongue and slinging them back into the mouth, 

 glued to its sticky tip. Its aim is unerring, but it never 

 strikes until both eyes come to rest on the prey, and great 

 accuracy of vision must accompany the great accuracy of 

 aim. Frogs and toads capture their prey in a somewhat 

 similar way ; and a great number of reptiles and amphibians 

 are absolutely dependent for their subsistence on the acute- 

 ness and accuracy of their vision, which is, however, on 

 the whole, markedly inferior to that of birds. 



In fishes, from their aquatic habit, the lens and dioptric 

 apparatus are specially modified, in accordance with the 

 denser medium in which they live ; and one curious fish, 

 the Surinam sprat, is stated to have the upper part of 

 the lens suited for aerial, and the lower part for aquatic 

 vision. 



Mr. Bateson * has made some interesting observations 

 on the sense of sight in fishes. He finds that in the great 

 majority of fishes the shape and size of the pupil do not 

 alter materially in accordance with the intensity of the 

 light. The chief exceptions are among the Elasmobranchs 

 (dog-fishes and skates). In the torpedo the lower limb of 

 the iris rises so as almost to close the pupil, leaving a 

 horizontal slit at the upper part of the eye. In the rough 

 dog-fish, the angel-fish, and the nurse-hound, the pupil 

 closes by day, forming merely an oblique slit. In the 

 skate a fern-like process descends from the upper limb of 



* Journal of Marine Biological Association, New Series, vol. i. Xos. 2 and 

 3. His experiments with regard to the colour-sense in fishes gave, for the 

 most part, negative results. 



