No. 382.] METHODS IN PLANKTOLOGY. 743 
described by him (Dolley, '96) : “ An apparatus which consists 
of a series of geared wheels driven by hand or belt, and so 
arranged as to cause an upright shaft to revolve to a speed of 
8000 revolutions per minute, corresponding to 50 revolutions 
per minute of the crank or pulley wheel. To this upright 
shaft is fastened an attachment by means’of which two funnel- 
shaped receptacles of one liter capacity’each, may be secured 
and made to revolve with the shaft.'» The main portion of each 
of these receptacles is constructed of spun copper, tinned. To 
this is attached the stem of the funnel, consisting of a heavy 
annealed glass tube of 15 mm. in outside diameter with a cen- 
tral bore of 2% to 5mm. These glasses are held in place and 
protected by a cover, such as is employed in mounting a water 
gauge. 
“ The receptacle having been filled with the water to be exam- 
ined, is caused to revolve for one or two minutes, when the 
entire contents of suspended matter in the water is thrown 
down to the bottom of the tube, from which the volume may 
be read off by means of the graduated scale on the outside of 
the tube. The plankton thus expeditiously secured can be 
transferred quickly to a vial or other receptacle, to be weighed 
or otherwise examined at leisure.” 
Power may be applied either by hand or through a belt by 
steam or electric motor. 
Our experience with the Planktonokrit indicates : 
(1) That two men on each crank cannot get a speed at the 
receptacle above 3000 revolutions per minute; a rate, however, 
sufficient to throw out everything except the Cyanophycezx. 
(2) The maximum speed must be continued for at least four 
minutes. ; 
(3) A speed much above 4000 revolutions with such a large 
quantity of water is dangerous, with the machine constructed 
as at present. 
This danger may be obviated : 
(a) By reducing the capacity of the receptacle. (500 cc. is 
probably sufficient.) 
(4) By lengthening the bearings of the upright spindle. 
