l893-] NEW-YORK MICROSCOPICAL SOCIETY. 91 



visit to the same spring, in the early part of September, I took 

 with me a one-ounce bottle with parallel sides and semi-cylindri- 

 cal ends, which form was useful in the subsequent observations. 

 Having in mind the subject of the motility of the brackish-water 

 diatoms of iMobile Bay, I desired to pursue the subject further 

 with a distinctly fresh-water variety of diatoms. The material 

 expressed from the algje of this spring I studied for five consecu- 

 tive days. 



On the evening of the day that I secured the Whistler material 

 I prepared a portion for examination, by repeated washings, 

 settlings, and changes of water, and then placed a drop on a slide, 

 when I found an abundance of living Navicula viridis — single 

 large individuals, and shorter ones grouped in fours and adherent 

 to each other. The first fact verified was that during the interval 

 between March and September the diatoms were still largely rep- 

 resented by the fourfold combination seen on my first visit to the 

 spring in March. 



The following is a resume of what I observed during a close 

 study of the living material. On the first night of my study I 

 sought to detect, if possible, the presence of the protoplasmic 

 mantle or sheath as demonstrated and observed by Cornelius 

 Onderdonk, and recounted by him in Ilie Micr>. scope (1890). 

 Having the living diatoms at hand, I made a concentration and 

 removed as much water as possible, in order not to weaken the 

 dye. I also had convenient a bottle of aniline violet ink. to use in 

 the attempt to differentiate the protoplasmic mantle as indicated 

 by Onderdonk. On adding a few drops of the aniline dye to the 

 living frustules, I quickly placed a drop of the diatoms on the 

 slide and covered the same with a three-quarter inch cover glass. 

 My surprise was great when I observed that the diatoms had 

 been instantly killed by the liquid. All that portion of the field 

 not occupied by the diatoms or debris gave no color indication. 

 After a fruitless search for any indication of an evident proto- 

 plasmic layer, I came to the conclusion that it was of such 

 exceeding tenuity that it did not extend sufficiently far from the 

 silicious frustule to indicate its presence at all. But the dye 

 took at once on the diatoms, and on every other particle of 

 matter, vegetable or otherwise. The only inference I drew from 

 this experiment was that the aniline paralyzed instantaneously the 



