COLLECTION OF BDELLOID AND OTHER ROTIFERA. 217 



will remain in good condition for some weeks, and thus provide 

 material for later examinations. If desired, some of the wet 

 moss can be placed in a glass jar with water, and this will live 

 well for some time. When an opportunity arrives for the ex- 

 amination of the moss stored in the metal box, a portion should 

 be placed in a wide-mouthed bottle of 4 to 8 oz. capacity, 

 and the bottle half filled with water. To dislodge any animals 

 attached to it, the moss is then stirred vigorously about with 

 the butt of a penholder or other suitable weapon, and afterwards 

 removed. After allowing the water in the bottle to settle, a 

 portion is poured into a stage trough and searched under a low 

 power for swimming species. The trough should be large enough 

 to permit of the introduction and free use of a fine pipette. If 

 no swimming species are present, or those seen are not wanted, 

 I pour away the greater part of the water from the bottle, and 

 after shaking up the remainder, refill the trough. The latter 

 is placed in a sloping position, so that the sediment may settle 

 on one side. When the water has fairly cleared, the trough 

 is transferred to the stage of the microscope (which, it is under- 

 stood, is inclined at a convenient angle), that side of the trough 

 on which the sediment has fallen being kept underneath. Any 

 Rotifera present will mostly be found moving among the sedi- 

 ment, and individuals desired for closer examination can be 

 picked out with the pipette. If the sediment lie thickly, it is 

 sometimes desirable, after some minutes in the inclined position, 

 to stand the trough upright, when most of the sediment will 

 fall to the bottom, leaving many of the rotifers attached to the 

 glass side. With a little care it is not difficult with the tip of 

 the pipette to push the rotifer from its hold without injury, and 

 to draw it into the pipette before it can regain its position. The 

 operation requires a little practice, as it must be done while the 

 trough is on the stage of the microscope. The trough is held 

 firmly with the left hand, and the pipette managed with the 

 right. For all preliminary work in searching through pond 

 gatherings or moss washings I use a 1-inch objective with an 

 A or No. 1 eye-piece. The further treatment of the selected 

 specimens will be described later. 



When the contents of the trough have been sufficiently searched, 



