90 JOURNAL OF THE [October, 



was explained by seeing another Nitzschia closter!um, having 

 attached to its exoplasmic layer foreign particles that were being 

 rapidly transported around its entire periphery, from the right 

 side around to the left, sometimes direct, sometimes alternating. 

 At another time I saw a small rotifer held a prisoner by a small 

 Navicula. At times the rotifer moved away a space equal to its 

 diameter, but was drawn back each time into a fresh contact with 

 the edge of the diatom, as if by some invisible force. While still 

 in contact with the Navicula, it drifted or was drawn between the 

 Navicula and an Amphiprora into a sort of cul-de-sac. I saw 

 also that under this mysterious fore? it vibrated rapidly between 

 the two diatoms — the rotifer, being inert, had not an independent 

 power of motion to release itself from its captors. In the drop 

 of water on the slide there were numerous and very active small 

 Naviculce, whose motions presented nothing of special interest, 

 except possibly that they often came in contact with larger Navi- 

 culce and passed by in contact with the protoplasmic sheath of the 

 larger diatoms, and soon parted company with them, as their 

 motion was swifter and not retarded by the sliding contact. This 

 will suffice to record such observations as were derived from a 

 painstaking study of material taken from the shore of Mobile 

 Bay and examined within an interval of six hours. 



Desiring to gather additional data bearing upon the behavior 

 of the living diatom under the lens, I had, about a week pre- 

 viously, secured some fresh-water diatoms directly from a natural 

 spring at the village of Whistler, Ala., five miles north of Mobile. 

 On a visit to the same locality in March last I casually found a 

 beautiful, clear spring flowing from a grassy, sloping hillside 

 into a barrel sunk flush with the grassy surface of the adjacent 

 ground. Selecting a small sample of the algge through which the 

 spring flowed away, I expressed the fluid therefrom on a spec- 

 tacle glass, and examined it with a pocket lens. I was surprised 

 to find the glass surface covered with a pure gathering of Navi- 

 cula viridis, all united in fours, or what I would call " tetradel- 

 phia." I then collected in a bottle a portion of the material and 

 took it to Mobile for examination as to the number and associ- 

 ation of species. But too much extraneous matter prevented a 

 suitable slide from being prepared, and the beautiful phenome- 

 non of the spectacle glass could not be repeated. On a recent 



