-^2 JOHNSON. [Vol. VIII. 



certainly a remarkable fact, and strongly suggests the possi- 

 bility that the supposed <' dwarfs" were in reality a dis- 

 tinct species, especially since no transitions were found 

 from the dwarf to the Stentor of normal size with moniliform 

 nucleus. 



C. Niitrition ; Alimentary Vortex. 



I have made a few observations upon the beautiful method 

 of capturing food prevailing among the Stentors — a method 

 of wide occurrence among the Infusoria, which Maupas has 

 fittingly termed the alimentary vortex ("tourbillon alimentaire"). 

 The appearance of the alimentary vortex is shown in Fig. 62. 

 The carmine-grains supplied in liberal quantity were eaten 

 freely, as the drawing clearly shows. The little arrows indicate 

 the direction of the currents created by the vibration of the 

 membranellae. It is impossible to detect the direction of the 

 "strong beat" of the membranellae by an inspection of these 

 organs in action, but it is revealed indirectly by the course of 

 the currents, which in turn are made manifest by the move- 

 ment of the carmine-grains. Since, then, the particles move 

 in an ascending curve to the left from positions of rest to the 

 right of the zone (when viewed, of course, from the dorsal side, 

 as in Fig. 62), and then sweep directly downward upon the 

 frontal field, we must infer there is some sort of suction 

 towards the frontal field, which could only be brought about 

 by a strong inward stroke of the membranellae. But this is 

 combined with another stroke, the direction of which is along 

 the zone towards the mouth. The result is that all particles 

 coming within the sphere of influence of the alimentary vortex 

 are drawn down to the frontal field, over the surface of which 

 (probably propelled by the motion of the minute cilia), they 

 glide towards the oral orifice. In 5. roeselii I have seen the 

 slow movement of nutrient particles along the marginal channel 

 characteristic of that species ; but in 5. cceruleiis, although the 

 elevated adoral zone (Fig. 62) effectually prevents the food- 

 particles from slipping over the edge of the frontal field, I 

 have not noticed that the carmine-grains took any particular 

 path on their way to the mouth. 



