598 EAYMOND PEARL. 



end of the pharynx^ the effect immediately following the 

 thnistiiig iu of the needle is a strong longitudinal contraction 

 of the whole body. After this first strong contraction the 

 animal remains perfectly quiet in the contracted form for a 

 varying length of time (in some cases as long as five minutes, 

 but usually less). After this period of quiet a series of 

 rhythmical waves of contraction pass longitudinally over the 

 still contracted body. The purpose of these waves is 

 evidently to loosen the restraining object by making the 

 hole in the body through which it passes lai'ger. This is the 

 same behaviour that I have observed in the deposition of the 

 large egg. This process of rhythmical longitudinal contrac- 

 tion is continued for a time; then the animal stretches to its 

 extreme lengthy attaches the anterior end to the substrate, 

 and attempts to crawl away. The movement of the anterior 

 end is precisely the same as in crawling. The animal turns 

 and twists and struggles violently in this attempt to crawl 

 away, and the cilia beat strongly. If the needle occupies a 

 position near the edge of the body this first struggle will 

 usually be sufficient to tear the body loose from the needle, so 

 that the animal may then move ahead freely. Such specimens 

 will, of course, have a large jagged wound in one side of the 

 body, which, however, closes in and heals in a short time. In 

 case the first struggle of the extended animal to craAvl ahead 

 is not effective, that is if the needle is too far in towards the 

 centre of the body to make the tearing out possible, the 

 animal, after continuing the struggle for a time, contracts 

 strongly longitudinally and goes through the whole series of 

 stages of quiet, rhythmical, longitudinal contraction and 

 attempted crawling again. The only difference between the 

 first and succeeding series of trials is that the stages in which 

 the animal is strongly contracted longitudinally tend to 

 become shorter with each repetition. 



In case the needle is thrust through the body in front of 

 the pharynx, the strong longitudinal contraction appears as 

 before, and is followed after some time by an extension of the 

 part in front of the needle, while the rest of the body re- 



