1893.] NEW-YORK MICROSCOPICAL SOCIETY. 95 



with the glass, while being examined with a moderately high- 

 power hand lens. 



This movement of the diatoms in contact with the smooth inte- 

 rior surface of the glass bottle will, I think, not yield to any other 

 interpretation, except that the gelatinous character of the envel- 

 oping protoplasm permitted them to adhere safely to the glass 

 without impeding their motion at pleasure ; and this is probably 

 why there was little or no evidence of the jerky or retrograde 

 motion often seen in a restricted field, as would appear under a 

 one-sixth lens. 



The facts developed here, and in the preceding account of the 

 motility of Amphiprora ornata, I propose to utilize in the closing 

 portion of these notes, when I will present my argument in favor 

 of the plea that the diatom has as much right to be regarded as 

 a protozoan as any of the other already acknowledged rhizo- 

 pods. I return for the moment to note additional studies of the 

 character of the motion of the large N. viridis. While contem- 

 plating the movements of a large specimen, I kept the diatom 

 constantly in the field to test even a suspicion of any sheath or 

 protoplasm covering. Noting very closely its perimeter, I was 

 able to distinctly make out that the diatom was surrounded by 

 a barely perceptible aureole, its outline being indicated by a row 

 of three or four minute particles of debris — not bacteria. These 

 remained continually at a permanent line close to one edge of 

 the frustule, leaving a hyaline space separating them from actual 

 contact with what would be regarded as the silicious edge of the 

 frustule. While still keeping my attention fixed steadily on this 

 line of minute debris, additional particles were gathered and took 

 their position in line with the others. But for this phenomenon 

 it would have been practically impossible to differentiate the ex- 

 tension of the gelatinous and pellucid covering from the surround- 

 ing water. 



On another occasion I watched the action of drifting bacteria 

 and other particles passed during the transit of the diatom. 

 These were constantly drifting by, either above or under the 

 frustule. Eventually the progress of the diatom was stopped for 

 a few moments by collision with a mat of debris, when a large, 

 motionless, gelatinous globule was arrested at its free extremity. 

 At the moment I recognized that the globule was under and in 



