COLLECTION, EXAMINATION, ETC. 311 



spaces as required. If the form is photographed, say, 

 from a diagram drawn up in Chinese white, the Hnes 

 in the positive will of course also appear white. The 

 forms can then be printed on ordinary bromide paper, 

 which will give a good dense black. The general 

 title and name of the formation to which the speci- 

 mens on the mount belong may be written on the 

 white card at the ends of the mount, and a number 

 given which wall refer to a list of the species it 

 contains, kept in an index register elsewhere. 



To attach the shells of Foraminifera to the 

 mounts, gum arable is most frequently used. A few 

 drops of glycerine should be added to an ounce of the 

 gum. This will prevent the gum from becoming 

 brittle and spoiling the shells by its fracture, espe- 

 cially when exposed to a very dry atmosphere. Better 

 than gum arable, however, is gum tragacanth, for 

 when this dries it is practically invisible on the 

 mount. To prepare it the gum should be steeped 

 in water until it swells, when it should be dissolved 

 in a little warm water until it is of the consistency of a 

 thin jelly. 



In mounting the minuter Foraminifera the sur- 

 face of the mount should be brushed over with a film 

 of gum, and when the object is transferred to it a 

 slight breathing close to the surface will deposit 

 sufficient moisture to cause the shell to adhere. 

 Larger Foraminifera may be cemented one by one 

 by placing little spots of gum where they are to be 

 affixed. 



The best brushes for the purpose of selecting and 



