454 journal of Comparative Neurology and Psychology. 



An amoeba is first hungry and moves, before it can react to food, 

 and so the more highly organized animal may exhibit its char- 

 acteristic behavior under external conditions which are uniform 

 and supply no stimulus to change of behavior, its energy over- 

 flowing in modes determined by the structure and changes in 

 internal conditions. 



SUMMARY AND CONCLUSIONS. 



1. Movements should be classified according to form. Classi- 

 fication according to direction into positive and negative, when 

 the form differs, is inadequate. For example, in Corethra the 

 positive reactions toward gravity, light and food differ in their 

 form. 



2. The movements of the larvae are discontinuous, each con- 

 sisting of a single lashing of the body and followed by an interval 

 of rest. For this reason the separate movements may be more 

 easily distinguished with reference to their exciting cause. A 

 single stimulus is followed by a single movement ordinarily. By 

 far the greater number of movements are pure overflows of energy, 

 adaptive in nature, since their asymmetrical character causes the 

 larva in a succession of such movements to face in all directions. 



3. Those movements which appear to be externally directed, 

 are characterized by precision and direct orientation with refer- 

 ence to the exciting stimulus. They conform in respect to the 

 mode of orientation to the peculiar adaptive action system of the 

 larva and are unconformable to the conventional mode of orien- 

 tation laid down in the tropism schema. 



4. The trial and error method is not exhibited in the orien- 

 tations to external stimuli. 



5. The horizontal range of these larvae is restricted, as their 

 ordinary movements involve little translation and some rotation. 

 They may move in a zigzag path, which is tolerably straight, 

 under stimulation. 



6. The vertical range involves daily depth migrations under 

 the combined influence of light and gravity. 



7. The larvae are positively geotropic and move downward 

 when the water is illuminated whether from above or beneath. 

 They move downward in the daytime on account of their positive 

 geotropism in strong illumination. They move upward in weak 

 light. 



