ing this end. It is always best to close the vessel used in such experiments 
to prevent the entrance of Algee not at the depth at which it is desired to 
take the samples or to keep some in the bottle from being lost in raising 
the bottle to the surface. In this way it is easily possible to obtain speci- 
mens that are floating from any part of the body of water. By this method, 
too, it was shown that numerous forms of Algze were distributed all through 
this body of water. The living ones were found in greater abundance at 
or near the surface, as would be expected, but they were also found in the 
deeper water as well. In some places the number of forms was often very 
small, but in order to make a study of the greater number from such a 
locality the following method was used: <A suitable quantity of water 
was obtained in the above described way from the desired location, and 
this allowed to filter through a small surface. A funnel, the lower end of 
whose tube was closed with closely woven cloth, served quite well, and in 
this way enough forms would be obtained for a convenient study. Such 
concentration of forms, we may term it, also brings about a great saving 
of time in looking for forms that would otherwise be found only after much 
searching, and at the same time was more representative for any given 
depth. 
The effectiveness with which various of the Algze forms could be re- 
moved by means of sand was attempted. This will vary with the kind 
of sand employed. The kind of sand here employed was very fine, white 
sand, especially employed for the microscopic examination of water. The 
following are some of the results: 
Twenty-five ccm. of water from the bottom of the reservoir, in five 
em. of this sand, required seven minutes to filter. 
One thousand ccm. of water from the surface of the reservoir required 
forty-three minutes to filter, through a closely woven cloth tied over the 
end of a very small glass tube. A considerable depth of very fine, clear 
sand is necessary to entirely remove all of the smaller Algre forms from 
the water, for I found after only twenty-five cem. of the water from this 
reservoir had been filtered through five ccm. of fine sand, a considerable 
number of some forms came through. In one instance, in tap water, com- 
ing from this same source, some small forms came through four cm. of this 
fine, white sand, which to filter twenty cem. it required one hour and twen- 
ty-five minutes. 
In another case only eighty-five minutes was required to filter twenty- 
five cem. of this water through four ¢m. of sand, due in this case to the less 
