024 SERGITJS MORGTJLIS 



a unit. A change in the position of one part of the worm's body 

 calls forth, immediately a coordinated response in a remote part 

 of the worm apparently due to an impulse passing from one end 

 of the animal to the other. 



Furthermore, these experiments show clearly that after some 

 vacillation the worm turns in the direction which allows it most 

 readily to maintain a straight course. The animal may turn to- 

 wards or away from, the source of stimulation, depending upon the 

 relative position of its tail. If the animal is stimulated on the right 

 side while its tail is bent to the left side, it recoils with a sudden 

 jerk to the right, i.e., towards the stimulus, until it has straight- 

 ened itself: then it creepsaway in the direction newly assumed. 

 But if stimulated on the left side it also swings to the right, i.e., 

 rhis time away from the stimulus, and begins to creep when nearly 

 in a straight position. Thus both reactions, towards and away 

 from the source of stimulation, are but incidents of the more fun- 

 damental reaction of orientation. Other movements likewise, 

 vaguely called random, may prove to be incidental to the spon- 

 taneous tendency of the worm to assume a straight course, and, 

 therefore, in studying the earthworm's reactions to stimuli of low 

 intensity this factor should be taken into consideration. 



BIBLIOGRAPHY 



Adams, (i. P. 1903 On the negative and positive phototropism of the earthworm 



Allolobophora foetida (Sav. as determined by light of different 



intensities. Amer. Jour. Physiol., vol. 9, no. 1, pp. 26-34. 

 Frikdlandkr. 13. 1^94 Beitriige zur Physiologie des Centralnervensystems und 

 Bewegungsmechanismus der Regenwi'irmer. Arch. f. d. ges. 



Physiol., Bd. 28, pp. 168-206. 

 II aki'kk. K. H. 1905 Reaction to light and mechanical stimuli in the earthworm 



Perichaeta bermudensis (Beddard). Biol. Bull., vol. 10. pp. 17-34. 



1909 Tropic and shock reactions in Perichaeta and Lumbrieus. Jour. 



Comp. Neurol, and Psychol., vol. 19. pp. 542-569. 

 Jennings, S. H. 1906 Modifiability of behavior. II. Factors determining 



direction and character of movement in the earthworm. Jour. Exp. 



Zool., vol. 3. no. 3, pp. 435-455. 

 Pabker. (I. H.. and Arkin, L. 1901 The directive influence of light on the 



earthworm Allolobophora foetida (Sav.). Amer. Jour. Physiol., 



vol. 4. pp. 151-157. 

 Smith. Amelia C. 1902 The influence of temperature, odors, light and contact 



on the movements of the earthworm. Amer. Jour. Physiol., vol.6. 



pp. 159 



