REACTIONS OF DIDINIUM NASUTUM. 



105 



come in contact with the water they form a mass which appears 

 to have a jelly-like consistency; and the increase of this mass 

 due to the extension of the trichocysts forces the two creatures 

 apart, but the attachment between them is not at once broken. 

 The seizing organ draws a portion of the ectosarc out, forming 

 a more or less marked protuberance and it is itself drawn out 



.- / T->.^'. , ;) v -^ TV^^V 



$m 



,^m 



H^ fty 



r. 



mih 



A fe ' '; 'S - 



^r\v ^ 

 I-X- ^ ; 



^^^j^mfev 



%W^ 



HJ^v^ ! 



12 



II 



FIG. n. A large Paramecium immediately after having been attacked by 

 a small Didinium. The discharge of the trichocysts has mechanically forced 

 the Didinium back, drawing the seizing organ out and producing a marked 

 protuberance on the surface of the Paramecium. 



FIG. 12. A Didinium entangled in a mass of trichocysts after the Para- 

 mecium attacked has escaped by tearing off the protoplasmic protuberance. 



FIG. 13. A portion of the seizing organ, S, left attached to the proto- 

 plasmic protuberance after the Didinium has escaped. The Didinium has 

 become free by twisting off the seizing organ. 



at the same time. If the Didinium is large and the Paramecium 

 small, the discharge of the trichocysts has little effect and one 

 sees but a small protuberance and only a slight extension of the 



