1893.] NEW-YORK MICROSCOPICAL SOCIETY. 89 



washings in water and by a special form of concentration I secured 

 a dip to examine on an uncovered slide. For a period of three 

 hours I watched the various living and moving diatoms, noticing 

 closely every condition presented by such as appeared, but seek- 

 ing especially to keep in the field an Amphiprora ornata, which is 

 one of the smallest of its genus, but sufficiently large to study 

 clearly. The same phenomena were presented as in the first 

 experiment, but with this variation: after observing a bacterium 

 that had touched the edge of the ala on the left side, it was oscil- 

 lated a few times alternately, and was then transferred along the 

 edge of the ala to the constriction, and then continuously across 

 the broad central portion of the frustule to the ala on the right 

 side, always along the periphery, and on to the opposite extremity 

 of the diatom, where it disappeared. Immediately after this a 

 good-sized, motionless rotifer drifted into contact with the left ala 

 and was rapidly rotated along the edge of the ala on the left side, 

 and was then carried to the middle constriction, where it was 

 retained some time, when it was rejected by the diatom. While 

 the rotifer was being manipulated on the left side a bacterium 

 was performing its oscillations on the right periphery, and what 

 appeared to be a cluster of bacteria were held prisoners above 

 and around the middle portion near the constriction of the alae. 



Another feature of interest attaching to the motion of Amphi- 

 prora is that in the event of its being capsized by striking some 

 obstacle in its path of motion, if thrown on its narrowest edge — 

 front view — it at once struggles to regain the position, which dis- 

 plays its side view, and then its motion continues direct and 

 rapid. This action intimates an intelligence akin almost to that 

 of a beetle on its back exerting itself to regain its natural position 

 on its feet. 



While shifting the field in order to observe some other indi- 

 cations of the life motions, I observed a simple, small Navicula 

 having in contact at one of its sublanceolate ends a Nitzschia 

 closteriiim — closely agreeing with Wolle's figure. The Navicula 

 seemed to be rapidly driving the Nitzschia, in the manner that a 

 violin bow is rapidly drawn by rising and falling strokes, or in a 

 see-sawing motion, while the Navicula was quiescent. This pro- 

 duced the illusion of the source of motion being situated at the 

 prow or apex of the Navicula. But a moment later the illusion 



