1893.] MICROSCOPICAL JOURNAL. 271 



the diatomist. In due time a mounted slide of this matter 

 came from Professor Smith with a note, saying that the diatoms 

 bel.mged to three genera, Nitzschia, Amphora, and Navicula — the 

 Nitzschia hnng the most and the Navicula the least numerous. 



A third jar in every respect the same as the second gave simi- 

 lar results It was thus made evident that the Hydroid had 

 nothing whatever to do with the results obtained. 



In another experiment two jars of the same size as the pre- 

 ceeding were taken. Into one of these jars a half litre of tlie 

 sea-water was drawn off at the top with the utmost care so as 

 to avoid roiling the water. The large vessel was then violently 

 shaken, so as to agitate the entire body of water, and at once, 

 while thus roiled, a half litre was put in the other jar; and both 

 jars set in the same eastern window. In two days, the turbid 

 water became perfectly clear, and on the bottom of the jar lay a 

 film of the mineral mud, with a few single valves of diatoms - 

 but not one entire frustule. 



In due time, both jars were carefully inspected. The one con- 

 taining the carefully drawn water gave no sign at the bottom 

 of the jar, and it required many dips taken for the microscope 

 to obtain even one diatom, which was a Navicula. In the jar 

 containing the water which had been roiled, on the thin pellicle 

 of mud at the bottom lay a large yield of diatoms. I thus in- 

 ferred that if undisturbed for a sufficient time the spores lay at 

 the bottom in the large vessel, and that a slight disturbance 

 might cause some to rise in the water. In both jars were a few 

 green uni-celled algse, doubtless from spores received from the 

 air. 



Using the same size jars, and in each the half litre of water 

 from the same source of supply, I resolved to vary the experi- 

 ments. The water was carefully and slowly filtered through 

 several thickness of chemist's filter-paper, the water before fil- 

 tering having been purposely roiled. The filter started with 

 passing 90 drops a minute, but took 90 minutes to filter a half 

 litre. The filter papers so used were set aside in a little water 

 to prevent drying. In the usual six weeks, or about, this fil- 

 tered water yielded the same rich crop of diatoms. 



Of the remaining experiments it must suffice to mention one. 

 The water in the vessel in the cellar was thoroughly shaken up, 

 and a litre of this roiled water was taken, and slowly filtered as 



