^'<^L-^] Bovard. — CondyJostoma patens. 359 



lying close to the substratum. The posterior end is enrved to the 

 left and closer to the substratum than the rest of the body. 

 During the motor reaction in the backward movement this end 

 is turned sharply to the left and often folded underneath, so that 

 it is hard to believe that the shape of the body while swimming 

 is any other than a natural one. This being the case, the spiral 

 swimming can easily be explained as a result of the form of the 

 body. The peculiarly curved end acts as a rudder and constantly 

 turns the animal froin the straight path, just as it does in the 

 simpler gliding movement. This seems to be the most important 

 factor of the three in a determination of the spiral swimming in 

 Condylo stoma. 



In swimming the rate of movement is more rapid than in 

 gliding. This conclusion is based on careful estiinates rather 

 than on accurate measurements. The rate of movement in glid- 

 ing is slower than in swimming, for it is during this time that 

 the animals are feeding. The friction with the substratum also 

 prevents rapid movement. 



III. MOTOR REACTION. 



Jennings ( '04) has found that the essential features of the 

 motor reaction are the same for each of the organisms which he 

 studied. It is the intention to give some facts which will show 

 that CondyJostoma acts as do other Protozoa in its general move- 

 ment but that the mechanism by which this action is produced 

 presents some distinctive features in this species. 



Of the two locomotor movements, swimming and gliding, the 

 latter is by far the most common, accordingly it is during this 

 method of locomotion that the motor reaction can be best shown. 

 While in the gliding position, the ventral side is close to the 

 substratum, the buccal groove faces toward the left and down- 

 ward, and the posterior end is bent somewhat toward the left. 

 Whenever an obstruction is encountered, the animal immediately 

 stops, backs up, turns to the right and then proceeds in a new 

 direction which generally will carry it pa.st the source of stim- 

 ulus. The movements of C. patens are not rapid and are easily 

 followed with the low power of the microscope owing to the large 



