CRAWLING OF YOUNG TURTLES TOWARD THE SEA 325 



his preliminary ('09, p. 124) and in his final report ('11, p. 70) 

 that the sun has nothing whatever to do with the direction in 

 which the turtles creep. 



During these preliminary trials it became perfectly evident 

 that the young turtles were very responsive to the slope of the 

 surface upon which they moved ; in other words, that they were 

 geotropic to a marked degree. Care was therefore taken that the 

 paper-board on which the tests were carried out was always 

 horizontal and attention was given to the geotropism of the turtles 

 as such. In all my experience the young loggerhead turtle was 

 always positively geotropic. It regularly goes down slopes, 

 notwithstanding the fact that it has ample energy and strength 

 to go up them, and it is responsive to even so slight an inclination 

 to the horizontal as 10°. On more considerable inclinations 

 the animals go down with a rush. Hooker ('11, p. 72) states 

 that "under ordinary circumstances the young turtles are nega- 

 tively geotropic, but if the possible descents have been exhausted, 

 they become positively geotropic." As a descent is evidence of 

 positive and not negative geotropism. Hooker has apparently 

 confused terms and, if this is so, his observations agree with mine 

 except that I have never seen any evidence whatever of negative 

 geotropism (movement against gravity). In all my tests of 

 turtles from the time of their hatching till the end of their first 

 week of life, they have been consistently positive in their geo- 

 tropism. When placed on the natural slope of a beach, even 

 though they cannot see the water, they travel downward at a 

 considerable rate. 



How they escape from the shallow nest in which they are 

 hatched I do not know, for I have never had the opportunity of 

 studying them under these circumstances. Newly hatched 

 turtles in the laboratory were from the beginning always positively 

 geotropic, so that I have no reason to believe that there is any 

 change in their geotropism. Such nests as I have seen were 

 always shallow, and it is quite possible that turtles on hatching 

 pass up their slopes and over their rims under other influences 

 than those having to do with geotropism and thus escape. But 

 concerning the details of this question I have no facts to offer. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGT, VOL. 36, NO. 3 



