106 



in day-time, and at the light of a lamp, I could not 

 observe any motion. 



Several Oscillatoriae creep only during the night 

 and in dark places. 



Upon many of them, as well as upon various 

 Naviculae and Frustuliae, light exercices a manifest 

 influence. When kept in cylindrical glasses , they 

 move towards the lighted side, and abandon the dark 

 one. I avail myself of this circumstance, when I 

 want to catch the finest specimens. When preserved 

 in china vases, filled with water, they reach very 

 soon the surface or the sides of the water, when 

 exposed to light. 



In day-time, the Surirella Venus closes more 

 its cuirass , which is never seen open but in dead 

 individuals. During the night, and at the weak light 

 of a lamp, I found many of them open, but they 

 closed quickly their valves , when I directed upon 

 them a more intense light. 



I have very seldom seen the points of the Pe- 

 diastra bending and moving themselves , and it is 

 equally rare to see the Closteria crooked 5 but these 

 motions were much more frequent in the animalcule, 

 when exposed to galvanic or electric strokes. 



