CERTAIN REACTIONS TO COLOR IN THE YOUNG LOGGER- 

 HEAD TURTLE. 



BY DAVENPORT HOOKER. 



During the summer of 1907 I made some observations of a very 

 preliminary and incomplete nature on the general habits and early 

 instincts of the young loggerhead turtle. A series of experiments was 

 performed with a view to determining the cause of the newly hatched 

 turtles reaching the water and the results obtained led me, at the time, 

 to believe that photophilism and negative geotropism were the elements 

 at work. In the summer of 1908 I repeated my experiments in a much 

 more thorough manner and extended the research greatly. From the 

 newer and more complete data obtained, I am convinced that I over- 

 looked certain very important factors in the environment and that 

 reactions to color and geotropism are the determining factors. I there- 

 fore take this occasion to correct what was said last year about photo- 

 trophism as such an all-important factor, though it certainly does play 

 some part, as my more detailed account will show. 



An idea of the locale of the experiments may be obtained from 

 fig. i. Pit A is on the northwest side of the island, some 30 feet from the 

 water's edge, and is overhung on the more easterly side by bay-cedar 

 bushes. Pit B, on the center of the point, is 10 feet in diameter and 

 about 4 feet deep, with sloping sides and the floor entirely out of sight 

 of any bushes or the ocean. The floor and walls are of sand. The shore 

 of the island is of coarse coral sand and free of vegetation. The deeply 

 shaded area shows where the bay-cedar bushes extend along the central 

 ridge of the island. 



The material used was afforded by three nests totaling about 300 

 turtles. These nests were surrounded by a high wooden pen which 

 prevented the escape of the young turtles and also prevented them from 

 seeing the ocean, the bushes, and the directive rays of the sun. The 

 young turtles were used as soon as possible after they had reached the 

 surface of the ground. In no case was the interval over 10 hours, while 

 in some instances they were helped out of the sand by gently raking it 

 with the fingers. There was absolutely no noticeable difference in the 

 response of the turtles kept 10 hours from those used immediately. 



EXPERIMENTS. 



When I was working on the young turtles in 1907, all my experi- 

 ments were performed in Pit A, and in the evening. At that time the 

 sun was in the west and the turtles all went west without exception. As 



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