Certain Reactions to Color in the Young Loggerhead Turtle. 75 



very slow in responding under such artificial conditions, their reactions 

 bear out the expectations for a positively phototropic animal. When 

 the light of a lantem is thrown at night into one of the pens containing 

 from 50 to 75 turtles, all orient and crawl toward the lantern and remain 

 in the area lighted by it. When in a large aquarium, all the turtles 

 coming within the area lighted by a lantern remain there and orient 

 toward the light. 



In 1907, I thought that the young turtles followed the sun in swim- 

 ming out to sea, but my more recent work has changed my opinion. 

 About 50 young turtles were let loose on the point (fig. i, P). All went 

 into the sea and swam 100 yards in their initial direction, then paused, 

 turned abruptly toward deep water and swam to it. By placing a simple 

 type of spectroscope in a water-glass and covering my head and the 

 bucket with a dark cloth, I was able to get very satisfactory "reflection 

 spectra," if they may be so called, of the sea-water at different depths. 

 This is a spectrum taken below the surface of the water and at a slight 

 angle below the horizontal. The results obtained were interesting in 

 that the deeper the water the greater the blue content of the light reflected 

 and vice versa. As the turtle swims with its head below the surface of 

 the water, it is quite possible that the greater blueness of the deeper 

 water attracts it. 



As a final test of the role played by any odor of the ocean water, a 

 glass bowl 1 8 inches in diameter was sunk to its rim in Pit B and filled 

 with sea-water. Turtles were placed one by one on its rim, some of 

 them having been immersed in it before being set down. While some 

 went into the water, many more turned away. They demonstrated no 

 definite tendency to go to it. The turtles behaved in exactly the same 

 manner that they did when there was nothing in the pit. This would 

 seem to indicate that there is no odor in sea-water that attracts the young 

 turtles. 



DISCUSSION. 



The general results obtained may be summed up as follows: 



(1) The newly-hatched loggerhead turtle moves away from trans- 

 parent and opaque red, orange, and green, and from green bay-cedar 

 bushes, and moves toward transparent or opaque blue. 



(2) After entering the water, the animal swims out to sea, apparently 

 attracted by the darker blue of the deeper water. The position of the 

 sun is an entirely negligible quantity. 



(3) When on the beach in a large sand-pit with level floor, from 

 which pit sight of the bushes and the ocean is excluded, but into which 

 the sun's rays shine directly, there is exhibited no definite tendency to 

 move in any definite direction. 



(4) Young loggerhead turtles are negatively geotropic, but when 

 all possible downward inclines have been exhausted they become posi- 

 tively geotropic. 



(5) Under a restricted environment the young turtle is photophilous 

 and responds to a large surface of light of low intensity rather than to 

 an illuminated point of high intensity. 



