1887.] MICROSCOPICAL JOURNAL. 45 
rection in which it is travelling. How is this done? If the motion of the 
diatom is caused by currents it produces in the water, then any sediment 
coming in contact with it should be carried from front to rear and there 
thrown off; precisely the contrary happens; a small piece of sediment will 
sometimes come against the side and be carried to the rear, then it is gener- 
ally taken up and carried back to the front over the top of the diatom, and 
may circulate back and forth in this way several times while the diatom is 
steadily moving on in one direction. None of the sediment or other matter 
appears to be disturbed by the passage of the diatom unless it comes in actual 
contact with it. 
In my previous communication* I mentioned dredging for diatoms in 
Morris’ Cove; perhaps some of your readers would like to know how I 
managed. I first went out with the oystermen and examined the sediment 
brought up on the oysters without finding anything rich enough to be satis- 
factory. I became convinced that the coveted forms were in the lighter ooze 
which was washed off before the dredge reached the surface. As I could 
find nothing else that would answer, and time was an object, I took a wire 
from a bale of hay, and by doubling and twisting it firmly made it sufficiently 
rigid to answer. I then bent it into a frame for the mouth of a dredge about 
eight by sixteen inches opening, with a handle to hold it in position when 
used, then fastening a bag or pocket of strainer cloth from the open mouth 
and a strong fishing line about one hundred feet long to the handle, I was 
ready for atrial. Being rowed out by a friend who was familiar with the 
cove, I had him stop where he said there was a muddy bottom, and threw 
over my dredge, starting the boat sufficiently to expand the pocket and get 
the dredge into the right position for work. I then paid out the line and let 
the dredge sink slowly to the bottom, then moved the boat carefully so that 
the dredge just skimmed along on the bottom; a little greater speed would 
have raised it entirely off on account of the resistance of the water. The 
very first trial was eminently successful. I saw, as soon as the dredge reached 
the surface, that I had what I wanted, and the first drop I placed under the 
microscope showed at least fifty forms of Plewrostgma, beside Coscinodts- 
cus, Actinoptychus, Campylodiscus, Auliscus, Navicula, etc. The Pleu- 
rosigmas were very active; there was little, if any, pause for rest—com- 
mencing their backward movement almost immediately. By the next morn- 
ing they formed a film on the sediment of a reddish brown color, and by 
pouring a quantity of the water into a wash-bowl I got a supply of them 
absolutely clean. A drop of this supply placed in the microscope was an 
astonishing sight; the field of view was filled with rapidly moving forms, 
crossing and re-crossing over and under and alongside of each other without 
ceasing. 
In subsequent trials of my dredge I found it necessary to wash it thoroughly 
at every cast, as the quantity of minute jelly fish caught so covered it with slime 
as to make it water-proof. I tried it outside the breakwater and light-house 
in the open sound, hoping to find larger forms. The water was here about 
fifty feet deep, and the mud softer than in the harbor. I found no Pleurosig- 
mas here, and the other forms were no larger than I had found inside; but 
there were multitudes of small forms. I placed this Slaaeaa a wooden 
water-pail to settle. In the morning I noticed a peculiar grahular appear- 
ance of the surface of the deposit, and on examination I found several inches 
of minute round clams. I skimmed off about two quarts of them without 
disturbing the sediment below and returned them carefully to their native 
element. They were about the size of pinheads. All the material procured 
* See page 37. 
