1893.] NEW-YORK MICROSCOPICAL SOCIETY. 87 



iield. On dr3'ing the glass I examined it, and was rewarded by 

 finding an abundance of diatoms, including a species which I 

 had nearly despaired of ever finding or seeing. This proved to 

 be Bailey's Amphiprora or/iata, as figured in his " Microscopical 

 Observations, etc., in 1850." During all the previous years of 

 my diatom researches I had desired to find Amphiprora of any 

 kind whatever, but apparently in vain. Having my " treasure 

 trove," I secured one full plant with its complement of mud, and 

 it is from this, and a second supply of the clean plants, that I 

 have prepared the series of six slides typical of the original mate- 

 rial that Bailey must certainly have examined, as he referred to 

 material often gathered from bogs or on shores where the diatom 

 ooze abounded. 



On the very same evening that I secured this moist water plant 

 I spent some hours in its examination, applying myself more 

 particularly to the character of the motion of the living diatoms. 

 It took me but a moment to find on the slide specimens of 

 living Amphiprora and Navicula. Confining my attention closely 

 to the appearance and structure of Amphiprora ornata, I was 

 enabled to observe that, if a bacterium drifted toward it and 

 made contact, it would be held as a prisoner in the full power 

 of the protoplasm covering the diatom externally. As is 

 well known through mounted specimens, as well as figures, 

 Amph'prora has delicate, hyaline, and rather broad alate lateral 

 processes. Bacteria and rotifers, once in contact with the 

 peripheral edges of the alae of the Amphiprora, are kept in a 

 ■constant state of alternate or reciprocal motion from either 

 diametrical extremity. That is to say, the bacterium or oher 

 organism is rapidly transported from the middle constriction to 

 one or other of the extremities of the diatom, all the way, or 

 part of the way, in an alternating manner ; when it may, after 

 an interval of detention, be rejected by what appears to be a 

 voluntary impulse of the Amphiprora itself. Having seen this 

 phenomenon, I at once became aware of its importance in any 

 discussion involving the plant or animal nature of the diatom, 

 and more particularly as all my previous acquaintance with the 

 Diatomaceae had permitted me to remain content with the gene- 

 rally accepted opinion that the diatom was " a lowly unicellular 

 plant." 



