IOO 



S. O. MAST. 



way and the mouths of the two creatures closed after quite a 

 considerable portion of the substance already swallowed had 

 flowed out. 



When the Didinia are numerous, several usually attack an 

 animal in rapid succession and it is very soon brought down with 

 a number of these voracious hunters firmly fastened to various 

 portions of the body, as represented in Fig. 9. 



Paramecia that escape after having been attacked once or twice 

 very frequently recover. On June 9, at 3 : 30 P. M., eight such 

 specimens were isolated and put into two watch glasses in a damp 



FIG. 9. A large Paramccium attacked by four small Didinia. Under 

 such conditions the Paramecium is usually torn in pieces and each Didinium 

 gets a portion. Sometimes however one Didinium gets the entire Para- 

 mecium, forcing the others off during the process of swallowing. 



FIG. 10. A large Paramecium which escaped after having been attacked 

 by a Didinium showing the wound, ?', the absence of cilia around the wound, 

 and a marked flexure in the animal, the result of contraction of the ectosarc. 



chamber. All the specimens were badly deformed, owing to the 

 violent contractions of the surface surrounding the wound. 

 Three died shortly after they were isolated, leaving two living 

 specimens in one watch glass and three in the other. At 10:00 



