340 



THE BIOLOGY OF THE FROG chap. 



a small red card which was moved near them. If a tuning 

 fork was sounded just before the card was presented, it 

 " became evident that the sound put the frog on the alert, 

 and, when the object came into view, it jumped at it more 

 quickly and a greater number of times than when the visual 

 stimulus was given without the auditory. . . . When the red 

 card was shown, it was often several seconds before the frog 

 would notice it and attempt to get it, but when the sound 

 also was given, the animal usually noticed and jumped toward 

 the moving card almost immediately." It is probable that 

 this habit of getting into readiness for a spring upon hearing 

 a sound near by is of value to the frog, since insects and 

 other creatures that serve as food often manifest their pres- 

 ence by some sort of noise before they come into the frog's 

 field of vision. If the frog prepares himself, he is more apt 

 to seize his prey when it appears. 



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