Collecting and Preparing Foraminifera 219 



cooling crystallizes, the formation of the crystals breaking 

 up the outer layer of the material. On being warmed, the 

 soda dissolves again in its own water of crystallization, 

 and the crystallization is repeated over and over again 

 until the lumps are broken up. The resulting mud is then 

 washed in the ordinary way. 



The best foraminifera from the chalk are those obtained 

 from the interior cavities of hollow flints. They are often 

 in the most perfect state of preservation, and the chalk 

 in these cavities being of a powdery nature, they are very 

 easily cleaned. 



The cleaned material should be sifted into varying 

 degrees of fineness, and each grade kept separately in a 

 tightly corked tube, noted with locality, date, and any 

 details as to the species contained in it, which may be 

 likely to be useful for future purposes of reference. If 

 the material has been properly cleaned and dried it can 

 be kept unaltered for an indefinite period, but if put away 

 damp fungoid growth will quickly set in. This can be 

 destroyed, and the material sterilized, by a prolonged 

 soaking in spirit, the material being afterwards dried 

 once more. 



To examine the material under the microscope, a picking- 

 out tray will be necessary. This is made by covering a 

 slip of card with coarse black-ribbed silk, the ribs running 

 longitudinally along the slip. A thin wooden ledge must 

 be glued round three sides of the slip to prevent the 

 forams rolling off when the stage of the microscope is 

 inclined at an angle. The material is sprinkled over the 

 slip, and the ridges of silk keep the forams from rolling 

 about. The specimens required can then be easily selected 

 by means of a fine sable brush, moistened by drawing it 

 between the lips, and transferred to a prepared cell or slip. 



The best fixative for mounting foraminifera is gum 

 tragacanth, which is almost invisible when dry, being 

 quite devoid of the objectionable glaze which characterizes 

 gum arabic. It is also much less subject to variations of 



