THE DEVELOPMENT OF AN INSTINCT 2 



- 1 t 



required for feeding was about 15 minutes per individual. It 



is worthy of remark here that, inasmuch as the death rate of 



the chicks was later found to increase with the length of the 



period of confinement, there seemed to be either a defect in 



our technique or a natural limit to this method of preventing 



practice. 



FIRST REACTIONS IN THE LIGHT 



When brought to the experiment table after their stay in 

 the dark-room, the chicks generally stood quiet and inert for 

 five minutes or more. The time recorded for one individual 

 was ten minutes ; for another, fourteen. To provide against 

 possible difficulties of light adaptation under which the ani- 

 mals might be laboring, the members of group III were allowed 

 to remain in the light from fifteen to thirty minutes before 

 the first tests were undertaken. During this interval they were 

 held by an assistant in order to prevent practice. The above 

 control proved fortunate in view of a later observation made 

 on the chicks of group V during their first few hours in the 

 lighted experiment room. When placed in a dark-lined box, 

 open at the top, half of which w 7 as shaded by the side of the 

 box nearest an adjoining window, these chicks crowded into the 

 shaded region. When moved repeatedly into the area of greater 

 light intensity, they as often returned into the shade. Direct 

 sunlight was excluded. Their phototropism had been reversed, 

 at least temporarily, by the previous confinement in darkness, 

 for chicks are known to be by nature positively phototropic. 

 Coupling with this the further fact that the animals blinked 

 noticeably on being first brought to the light, one may be in- 

 clined to conclude that the eyes of the animals were abnormally 

 or pathologically affected during the first tests. However, even 

 when special measures were not taken to adapt the chicks, the 

 period of inactivity at the start gave considerable if not suffi- 

 cient opportunity for adaptation. Furthermore, it is improb- 

 able that the normal accuracy of vision in these chicks was 

 mpaired, for their first records, compared with those of the 

 standard group, show even a smaller average number of " miss- 

 ing" reactions. 



During this period of inactivity they devoured with apparent 

 relish food that was inserted in their mouths, and even excitedly 

 gave the food twitter when thus fed. But left to themselves 



