478 R. T. YOUNG 



resemblance between it and the bellies of the mice was correspondingly 

 lessened. Within ten minutes one mouse was taken from the clay. The 

 mouse taken in this experiment was nearer the baseboard of the cage 

 than the other two on the clay. On this baseboard the owl frequently 

 alighted after flying across the cage from its perch. 



Experiment 5. Same as Experiment 4, except that only one mouse 

 was placed on the earth. Within thirteen minutes it was taken from 

 the latter. 



Experiment 6. Figures 8 arid 13. Six mice were placed on gypsum 

 and six on moist clay mingled with leaves, straw, etc,-* Almost im- 

 mediately the owl flew directly to the gypsum and took a mouse 

 therefrom. 



Experiment 7. Same as Experiment 6, with same result. 



Experiment 8. Same as Experiment 6, except that only four mice 

 were placed on each background. In six minutes, the owl flew directly 

 to the gypsmn and took a mouse from it. 



Experiment 9. Figure 14- Four mice were placed venter upper- 

 most on moist earth, and four on clay, the backgrounds being suffi- 

 ciently excavated to bring the bellies of the mice flush with their sur- 

 faces. The relative positions of the backgrounds in this experiment 

 was again reversed to the original position. Within twenty-four min- 

 utes one mouse was taken from the earth. 



Experiment 10. The same as 9, but position of backgrounds re- 

 versed. The following morning I found four mice removed from the 

 earth and one from the clay. 



Experiment 11. Figures 8 and 11. One mouse was placed on gyp- 

 sum and one on leaves mixed with moist earth and clay. Within 

 five minutes, the mouse was taken from the former background. 



Experiment 12. Same as Experiment 11, except that the back- 

 grounds were reversed in position. The owl flew back and forth across 

 the cage several times, twice alighting on baseboard of cage nearest 

 the background of earth and leaves. In about ten minutes it alighted 

 on the baseboard a third time, remaining there for ten or twelve minutes 

 more. Soon after (exact time not recorded) the mouse was taken 

 from the gypsum. Sometime during the night the mouse was taken 

 from the leaves. 



Summary 



In eleven out of twelve experiments or 92 per cent the combi- 

 nation of greater contrast was chosen, and in the other experiment 

 (4) the resemblance between the mouse chosen and its back- 

 ground was not great, and the owl probably alighted nearer 

 to it than the other background before feeding. 



^' In this and the two succeeding experiments, the position of the light and 

 dark backgrounds was the reverse of that in the preceding experiments. 



