Yerkes, space Perceptio7i of Tortoises. 



23 



tion to seek escape, and, in the case of the water tortoises, to 

 seek the water, but as it is pushing over the edge the visual 

 impressions of distance initiate a conflicting motor impulse 

 which causes the animal to draw back. This species manifests 

 fear much more markedly, frequently, and at a less height than 

 does C. picta. On the whole we may say that its behavior to 

 spatial relations would ordinarily be interpreted as indicative of 

 more accurate space perception. 



At none of the three heights used in the experiments does 

 Terrapene Carolina push over the edge without some hesitation 

 and manifestations of fear. At 30 cm. almost all individuals 



TABLE III. 



Terrapene batiri 

 Taylor 



Behavior much the same as that of T. Carolina. 

 There is careful inspection of the surroundings and 

 long hesitation. One individual was found that 

 plunged off directly at the height of 180 cm. 



Xerobates poljiyhemus 

 Daudin 



Examination of edge as in T. bauri. Hesitation at 

 30 cm., and great fear at i8o cm. 



Testudo vicina 

 Gilnther 



Not afraid to fall 30 to 50 cm. but careful when at 

 greater heights. 



Chelopus ivsculphts 

 Laconte 



This species shows greater hesitation than does N. 

 guttata. At 30 cm. it examines the surroundings, 

 and often fails to leave the board. 



Emys tneleagris 

 Shaw 



In this species there is some hesitation at 30 cm. but 

 seldom failure to go off. At 180 cm. there is marked 

 fear as in N. guttata, which it very closely resembles 

 in its behavior. 



Chelodiiia noz'aehollan- 

 diae Dumeril et Bibron 



Although this form carefully examines the edge and 

 looks at the floor intently it seldom fails to go off. 

 Its actions are very deliberate in most cases. 



Trachemys scabra 

 Agassiz 



Many indiduals pay no attention to the edge Lit- 

 tle hesitation even at 180 cm. Behaves much like 

 C. picta. 



Podocneniis tnadagas- 

 cariensis Grandidier 



No hesitation, no fear at any height at which it was 

 tried. Pays less attention to spatial conditions than 

 any of the species -studied. 



