HABirS AND REACTIONS OF LACRYMARIA 237 



CLEANING REACTION 



One frequently sees specimens of Lacrymaria with the neck 

 extended and curved on itself so as to bring the head in contact 

 with the body over which it passes back and forth lengthwise 

 occasionally several times in succession but usually only once 

 or twice. Fig. 6. The rapid movement of the oral cilia during 

 this process makes it appear as though the surface of the body 

 were being thoroughly cleaned. It is, however, probable that 

 in this reaction the head is merely running over the body as 

 it would over any other object under similar circumstances. 



REGULATION OF THE MOVEMENTS OF THE HEAD 



The center of interest in the activities of Lacrymaria lies in 

 the movements of the head. How^ is it possible for an organism 

 to extend its neck in all directions eight times the length of 

 the body, fifty times its own length, and while thus extended 

 to turn the head rapidly and extensively in all directions, making 

 curves and sharp angles in the neck, bending it on itself and 

 the like, and then to contract the whole so that it disappears 

 almost entirely in the body? Figs. t,-S. 



It has generally been assumed that the anterior end of Lacry- 

 maria is forced out by a sort of peristaltic circular contraction 

 of the tissue in the neck and that its lateral movement is pro- 

 duced by unequal longitudinal tension on opposite sides, that 

 the movements of the neck and head are regulated much as are 

 those of the tentacles of Hydra or those of an attached Stentor 

 on its stalk. This, however, is in all probability not true. In 

 the first place it seems impossible that circular contraction 

 could force tissue out to such an extreme distance compared 

 with the diameter of the organ involved and at the same time 

 admit of such free lateral movements as are found in this 

 animal. And in the second place, to account for the formation 

 of sharp angles in the neck with the tissue on either side of the 

 angle straight as represented in Fig. 7, it must be assumed 

 that unequal tension exists only between the body and the place 

 where the angle is formed, and that the neck beyond the angle 

 is rigid enough to swing the head from side to side without 

 bending, a condition which seems quite impossible. We must 

 consequently look elsewhere for an explanation of the phe- 

 nomena in question. 



