180 



S. R. DETWILER 



The tortoises were allowed sufficient time to recover from the 

 effects of the operation before they were placed in light or dark- 

 ness. Two operated animals were always used together for 

 experiments and as controls two normal animals. All were 

 placed in darkness for 24 hours, at the end of which time 1 oper- 

 ated and 1 normal individual were selected and placed in sun- 

 light for 7 hours after which the eyes of all were removed and 

 fixed as above described. 



Upon examination and comparison of sections, it was seen 

 that the pigment of the operated light eye had migrated for- 

 ward and indeed further than it had in the normal eye of the 

 same animal and in the eyes of the controls (figs. 2 and 3, 

 and tables 1 and 3). Moreover that the cones had contracted 

 about as much as in the normal eyes (see tables 1 and 3). 



TABLE 31 



' Based on 10 measurements as in tables 1 and 2. 



Now when the dark eyes of the operated and the control 

 animals are compared, it is found that the pigment of the ope- 

 rated eyes is further forward than in the control eye of the same 

 animal and in the eyes of the control animals. In fact the 

 position of the pigment in the operated dark eye is about as far 

 forward as it is in the normal light eyes (figs. 2 and 4, and tables 

 1 and 3). These results also show that the cones contract in 

 light when the optic nerve is cut (table 3). Moreover, by com- 

 paring tables 1 and 3, it will be seen that the cones are longer 

 in the operated dark eye than in the normal dark eye These 

 results would seem to be in line with those of Herzog ('05) who 

 found that destroying the central nervous system of the frog 

 brought about in the dark eye examined immediately or 24 

 hours later, a maximal forward migration (light position) of the 



