EXPERIMENTS ON PROTECTIVE COLORATION 461 



Experiment 4- One specimen of pipiens was placed on grass and 

 one on sand. After more than half an hour, a crow dropped and picked 

 the frog from the grass. 



Experiment 5. One specimen of pipiens was placed on mud and one 

 on sand.^ In a few minutes a crow dropped on the mud but took the 

 frog from the sand. 



Experirnent 6. One cantabrigensis was placed on sand and one on 

 mud.^ After considerable delay, the frog was taken from the sand. 

 In this experiment particularly it appeared very probable that the crow 

 saw the frog before dropping to seize it, as it turned its head from side 

 to side examining the floor of the cage before doing so. 



Experiment 7. One cantabrigensis on mud and one on sand.^ The 

 former was seized by a crow directly after dropping and with little 

 inspection. 



Experiment 8. One pipiens oh sand and one on grass. Former taken. 



Experiment 9. This was a repetition of Experiment 8 and the same 

 results were obtained. The frog was seized by the crow directly on 

 alighting. 



Experiment 10. One pipiens on sand and one on grass. Former 

 taken. 



Experiment 11. Same as Experiment 10. 



Experiment 12. One pipiens on grass and one on sand. Former 

 taken. In this experiment the frog was apparently not seen until 

 after the crow had alighted, as the latter started to walk to the opposite 

 side of the cage and was very close to the frog on the grass before ap- 

 pearing to see it, when it stopped and seized it. 



Summary 



Thus in nine of these twelve experiments, or in 75 per cent, 

 the frog was taken from that background with which it formed 

 the better contrast, while in one of the remaining three, the differ- 

 ence in contrast between the two backgrounds was not marked.*^ 



SERIES II 



Plate 2, figures 39 and J^l 



In this series also a crow was employed as the preyer and 

 crickets (Gryllus pennsylvanicus) as the prey. The crow was con- 

 fined in a cage 5.0 x 2.4 x 1.5 m. in size, at one end of which was a 



5 In this experiment the frogs died, changing color from green to dark olive 

 after being stunned. 



•* A high wind was blowing during this experiment and the sand was driven over 

 onto the mud and altered the color of the latter to a considerable extent. 



