144 HOW TO PREPARE FORAMINIFERA. 



This Paper would be incomplete without a few practical hints 

 as to how to examine the floatings, etc., for the Foraminifera. 



The microscope must be used all but, if not quite, upright, — 

 the latter is best, though rather awkward. If furnished with 

 rectangular motions, such may now render good service ; but these 

 are far from being essential, and, in fact, a simple arrangement of 

 a sliding stage and tray, which may be made by the student, will 

 answer every purpose and do first-rate work. 



A tray of some sort is necessary, and may be easily made of a 

 piece of thin slate, say 4 inches by 2 J inches, rubbed down 

 perfectly flat on each side ; but I much prefer a tray made of 

 black ferrotype-plate, 4 inches by ij inches, with the edges on 

 each side, and one of the ends turned up neatly about Yifith of an 

 inch. On this tray must be spread as thinly as possible, by gently 

 shaking from a pill-box or spoon, a layer of the " floatings " or 

 other washed material, for examination. The tray must then be 

 passed regularly to and fro across the stage of the microscope, in 

 such a manner as to ensure the examination of the whole of the 

 surface, without needlessly going over any part twice. This may 

 be easily done by commencing at the side furthest from us, and 

 moving the slide from the right to the left. Then move the slide 

 azvay a distance equal to the width of the field of view, and 

 returning it again to the right, examine a second time while 

 passing //w;/ right to left. It is better to have a definite plan as 

 here given, and not to work left to right and right to left, but only 

 one way, and I believe pushing the tray f?'om the right to the left 

 will be found most convenient. The shells should be picked out 

 with the sable pencil, as before described. The lower the power 

 of the objective the better, and it is rarely needful to go higher 

 than one inch. 



Of all ways of mounting Foraminifera, none is to be com- 

 pared with mounting them as opaques. When mounted in 

 balsam, as transparencies, it is almost, if not quite, impossible to 

 identify the different species. Foraminifera look best without a 

 covering-glass ; hence, a cell which admits of the cover being 

 removed without injury is to be preferred. These may readily be 

 made by selecting ebonite rings of such sizes as that one will fit 

 just inside the other ; the smaller one should be well cemented 

 to the glass slip, and the cover be fixed on the larger one. Ward's 

 " Brown Cement" is first-rate for the purpose, but old Gold-size will 

 do. Cells made of thick cardboard with a hole punched through 

 one piece, which is then pasted to a second, with a piece of black 

 paper under the hole, are very useful and easily made, and are 

 largely used. Section-making scarcely belongs to the purpose of 



