VOL. XV.] NESTLING WILLOW-WARBLEK. 5 



of the nest, and with its head directed towards the nest. 

 It turned through an angle of 45 degrees away from the nest, 

 and went obhquely past the nest for a distance of six inches. 



5. A chick was placed directly in front of and looking 

 into the nest. It turned round through an angle of rather 

 less than 180 degrees and moved away from the nest. 



That distance from the nest, within the limits of the 

 experiments, was not an important factor is shown by the 

 next two tests. 



6. A chick was placed at a distance of two feet from the 

 nest. It did not move within eight minutes. 



7. Another chick was placed at a distance of three inches 

 from the entrance to the nest. It did not stir at all in five 

 minutes. On being restored to the nest, this chick had to 

 be held there for some time by hand, as twice it turned round 

 and crawled out of the nest. 



In these tests there is one factor in common — the turning 

 movement made by the chick when it finds itself outside 

 the nest. 



This movement is directed in the right sense when the 

 chick faces away from the nest, and is, therefore, adaptive. 

 Chicks may sometimes find themselves out of the nest. In 

 this event they are most likely to be oriented as they were 

 oriented in the nest. Their only chance of survival is then 

 to turn round and crawl back into the nest, since there is no 

 evidence that the parents give active assistance. That the 

 turning movement is a fixed and inherited, though far from 

 perfect, reaction, is shown by the second series of experiments 

 in which the chicks placed facing the nest turned round and 

 went away from it. This series also shows that the chicks 

 do not have a sense of passive rotation. Only in one case 

 was the turning movement perfect ; in all the other cases 

 it was inadequate to produce correct orientation towards or 

 away from the nest. 



