REACTIONS TO LIGHT IN THE EARTHWORM. 3! 



trouble to make random movements but begins to burrow into 

 the soil immediately. After heavy rains we see them washed out 

 of their burrows, and crawling in unwonted places when they are 

 unable to burrow. 



REACTIONS TO MECHANICAL STIMULI. 



Pcric/ueta goes through its peculiar jumping movements only 

 under mechanical or similar stimulation, never under the influence 

 of light, so far as we have observed. When touched with a 

 needle on the anterior end it contracts the anterior segments 

 slightly and may begin to crawl backward or it may go forward, 

 lifting its head and making various random movements before 

 settling on any direction. With a slightly stronger stimulus the 

 anterior end turns away slightly from the stimulus. Increase the 

 stimulus and the worm may contract the longitudinal muscles of 

 the opposite side so as to jerk the body around 90 or even 180 

 degrees, and so give it a new direction. Or the worm may go 

 off into a whole series of jerks, so that there is a complete grada- 

 tion between the extent of the responses, depending upon the 

 stimulus. More important as determining the extent of the 

 reaction is the condition of the worm. Well-fed worms in fresh 

 condition, when just dug out of their burrow, spring around in 

 the liveliest fashion. If handled they give a series of movements 

 which must make it difficult for an enemy, a bird, for instance, to 

 pick them up before they get a chance to crawl under cover. 

 When stimulated they exude an abundant yellowish mucus. 

 Whether this is an offensive secretion to its enemies is not known 

 to the writer. When a point in the middle of the worm is stimu- 

 lated the body recoils away from the stimulus at that point and 

 there is a slight swelling due to contraction of the longitudinal 

 muscles, like the contraction and shortening of the anterior end 

 under stimulation. Occasionally the worm may move violently 

 toward the stimulus, but this seemed to be due to an overstimu- 

 lation producing a complex of effects rather than a simple reflex. 



The leaping movements of Pericli<zta are certainly the best 

 examples of random movements that are afforded. They are 

 exclusively adapted to those chance circumstances when the 

 worm gets out of its burrow. They lead in no definite direction, 



