134 J- PAUL VISSCHER. 



reacted much more violently than previously and at the point of 

 contact a noticeable bulging of the protoplasm occurred. The next 

 attack was at a new spot, with the characteristic discharge of 

 trichocysts. But the following one was at approximately the same 

 spot as the preceding. The protoplasm this time bulged out and 

 formed a large protuberance, even some of the zoochlorellae flowing 

 out into it. After half an hour four such protuberances were 

 observed, in all of which it was evident that the pellicle of the 

 paramecium had given way at one small spot, and that the mass of 

 protoplasm which flowed out formed a protuberance with only a 

 narrow connection with the interior. . After repeated attacks the 

 paramecium disintegrated. 



The other paramecium, meanwhile, had slowly moved toward the 

 dileptus, and this afforded an opportunity to repeat the observations 

 just described. The results obtained in these observations were 

 essentially the same as those obtained in the first observation. 

 The second paramecium, however, appeared to react more vigor- 

 ously and it consequently escaped more of the attacks than the 

 first, with the result that at the end of half an hour it had only two 

 protuberances, whereas the first, as previously stated, had four. 

 Apparently each attack on the part of the dileptus was just as 

 powerful at the end of the experiment as it was at the beginning. 



b. Effect of Trichocysts on Stcntor cceruleus. 



Perhaps the most instructive, at least the most spectacular, ex- 

 periment concerning the action of the trichocysts of Dileptus is 

 one which can be performed very simply as follows : A dozen or 

 more dilepti are starved for two days ; a large blue stentor is then 

 introduced, and the scene of a veritable barbecue is soon presented. 

 The dilepti collect about the stentor and can be seen to strike the 

 latter with their proboscides (Fig. 5). The surface that comes in 

 contact with the stentors in this reaction does not appear to be 

 purely accidental, for it was observed that the oral surface of the 

 proboscis came in contact almost without exception. At the point 

 of contact the pellicle of the stentor gives way momentarily (Fig. 

 5, D, d}, and a globular mass of protoplasm is extruded. This 

 mass is soon constricted off (Fig. 5, F, b), and the wound appar- 

 ently heals over at once, while the extruded protoplasmic mass is 



