COLLECTING AND MOUNTING ROTIFERA. 327 



these cells on the centre of a cavity cell slide and placed the slide 

 on a metal table with spirit lamp underneath, which could be 

 H'emoved occasionally until I could see that the cement adhered 

 all round. Great care must be observed that the heat be not 

 too great or bubbles will appear in the cemented ring. 



The slides thus prepared can be put aside till wanted. When 

 the time arrived I used to run a ring of Clarke & Page's cell 

 cement on the clean surface of the glass cell, and allowed 

 this to dry for twelve to twenty-four hours. Having pre- 

 viously selected a cover- glass which very slightly overlapped 

 the diameter of the cell, say by not more than y\- inch or J^ 

 inch, I filled the cell with the mounting fluid (2i per cent, 

 formalin) and placed in it the prepared specimen, leaving 

 it there for a short time so as to enable me to prick any 

 air-bubbles with a needle or single hog's bristle. I then filled 

 the cell just full with as little as possible of this fluid and 

 placed one drop of fluid on the cover-glass, which was lowered 

 on to the cell and adjusted, using hardly any pressure, the 

 surplus fluid being taken up first with a pipette and then with 

 thin blotting paper or cigarette paper. After two or three hours' 

 time it will be necessary to examine the slide under the preparing 

 microscope to see that the cover is properly sealed all round 

 the edge, and, if need be, to add a drop of cement. If this is 

 found quite satisfactory the slide can be put aside for three or 

 more days, when further coats of Heath's or Clarke & Page's 

 or Flatters & Garnett's cement are to be added, leaving each 

 €oat three days to dry before adding the next.* 



Bibliography. 



1889. On a Simple Tank Microscope, Journ. QueJcett Micr. Club, 



Ser. 2, vol. iv., pp. 53-54. 

 1892. On the Best Methods of Examining Rotifers under the 



Microscope, Trans. Middlesex Nat. Hist. Soc, pp. 23-30. 



* My slides of Rotifera and Polyzoa were presented to the Natural 

 History Section of the British Museum at South Kensington, where 

 they may be examined on apph cation to the curator. 



