354 THE BIOLOGY OF THE FROG CHAP. 



frogs would go hungry. Subsequently I placed a large fly 

 upon a piece of thin mica, and surrounded it with a circle 

 of fine needles, piercing the plate. The fly thus protected 

 could only be seized by the frog suffering a severe pricking 

 of the jaws. This I found a frog would suffer indefinitely 

 in its attempts to secure the fly. In one instance the frog, 

 which had been fasting for seventy-two hours, continued to 

 snap at the needle-protected fly until it had entirely skinned 

 its upper jaw. I concluded from this that the wits of a frog 

 were too limited to be demonstrated." 



Knauer finds that frogs persist for a long time in snapping 

 at worms from which they are separated by a glass partition 

 without becoming aware of the futility of their efforts. They 

 will keep up their endeavors at intervals all day ; how much 

 more time would be required to convince them that their 

 efforts are vain is uncertain. 



Wood frogs, according to Abbott, exhibit much more 

 ingenuity in the pursuit of prey than the ordinary aquatic 

 species. "I have frequently noticed," says Abbott, "when 

 I placed flies in the case, that the wood frog singled out 

 one and approached it in a very stealthy manner, squatting 

 closely to the moss, hiding behind ferns and dragging itself 

 along, until it had reached a position suitable for making 

 a successful leap. If the fly moved, the frog would alter 

 its position accordingly, and follow up the chase with great 

 patience and unquestionable skill. At times it would happen 

 that some one of the smaller batrachians kept in the case 

 snapped at the coveted prize, when the disgust of the wood 

 frog would be plainly shown by its manner, but such an 

 occurrence never led to a quarrel." 



Frogs, when liberated, are generally credited with making 

 for water by the nearest route, but Abbott finds that this is 

 by no means always the case. Frogs tend to keep near 



