J. PAUL VISSCHER. 



is added to gelatine, but very much more rapidly. This mass was 

 usually constricted off from the remaining part (Fig. 4, B, b), 

 sometimes immediately, sometimes later. If this occurred imme- 

 diately, the portion constricted off was carried to the gullet by 

 ciliary currents and engulfed. Otherwise this portion was dragged 

 along for a longer or shorter period by the active portion of the 

 Colpidium (Fig. 4, c, e). Most of the Colpidia which were in- 

 jured in this way soon died. Only a few of those which were 

 isolated survived, and these had apparently lost only a small portion 

 of their cytoplasm. 



FIG. 4. Sketches illustrating the effects of the trichocysts of Dileptus on 

 the infusorian Colpidium. A, B, and C, successive stages in the process of 

 feeding, a, colpidium (motionless after contact with oral surface of pro- 

 boscis) ; b, portion of colpidium (apparently cytolyzed and separated from 

 major portion, c) ; d, cytolyzed portion being engulfed by dileptus ; e, major 

 portion of colpidium swimming rapidly away. 



It seems evident from many observations like the above that it 

 is the trichocysts of Dileptus which function primarily in the cap- 

 ture of Colpidium. The colpidia are first momentarily paralyzed 

 'and then excited to vigorous reaction, but as a rule only after a 

 part of their cytoplasm has been in some way altered so that it 

 disintegrates and Dileptus is enabled to feed on it in the same way 

 that it does on other non-motile material. 



The results presented seem to indicate that in Dileptus there are 



