280 



MOTOR RESPONSES 



transformations at the posterior end. Moreover, the shock reactions ap- 

 pear to be associated with rapid local increases in the sol-gel transforma- 

 tion. If the views concerning the process of orientation as presented 



Figure 97. Camera outlines representing different stages in the process of orientation 

 in Amoeba protens. 1, Amoeba oriented in light /'; 2-9, successive positions after ex- 

 posure to light /, time indicated in each. Arrows represent the direction of streaming 

 of protoplasm in the pseudopods. In those which do not contain arrows there was no 

 perceptible streaming at the time the sketch was made. / and /' direction of light; mm, 

 projected scale. (After Mast, 1910.) 



above are correct, it is obvious that orientation is the result of shock 

 reactions rather than kinetic reactions. 



B. FLAGELLATES 



Response to rapid changes in the intensity of light is very widespread 

 among the flagellates, and many of them orient fairly precisely. The 

 processes involved are essentially the same in all. Euglena is representa- 

 tive of those which orient, and Peranema trkhophorum is representative 

 of those which do not. 



Euglena rotates continuously on its longitudinal axis as it swims. The 

 flagellum extends backward along the ventral or abeyespot surface. This 

 causes continuous deflection of the anterior end toward the opposite 



