264 H. S. WILLIS. 



microscope was 29.5 C. The results obtained are in part re- 

 corded in Fig. 3. It may be observed fronTthis figure that the 

 nucleated part moved from the light and that with each change 

 in the direction of the rays of light, there was a corresponding 

 change in the direction of the movement of the segment, while 

 on the other hand, there was no indication of orientation in the 

 enucleated fragment. The two parts were subjected to precisely 

 the same conditions throughout the entire experiment. 



As previously stated, there was usually no indication whatever 

 of orientation in enucleated segments, and it is questionable 

 whether any of these parts actually oriented, yet, in a number 

 of cases, slight movement from the light occurred, and in three 

 cases there was a change in the direction of movement with a 

 change in the direction of the light. This movement from the 

 light may have been a reaction to the light in the form of orienta- 

 tion or it may have been merely an accidental movement made 

 without regard to the light. The facts regarding the three cases 

 are these. One of the segments, while moving at right angles 

 to the light, formed a pseudopod on the shaded side, and move- 

 ment occurred in the direction of the pseudopod. With a change 

 in the direction of the light, a short pseudopod was formed again 

 on the shaded side, but at this point the fragment assumed a 

 globular shape. In another segment movement occurred for 

 several seconds at right angles to a horizontal beam of light, then 

 the direction was changed, and the fragment moved from the 

 source of stimulation. Upon a change in the direction of the 

 light, this fragment changed the direction of its course and again 

 moved from the light for approximately one minute and then 

 became globular. In the third enucleated segment substantially 

 the same reaction was observed. If these fragments actually 

 oriented in response to the light, the process of orientation in 







them was essentially different from that in nucleated fragments. 

 There is, therefore, a difference in nucleated and enucleated 

 parts of Amoeba in their response to light as well as in the char- 

 acter of their movements; but there is also a difference in the 

 rate of locomotion as will be demonstrated presently. 



