TECHNIQUE 67 



potash. After immersion for a few hours, the alkali can 

 be neutralized with hydrochloric acid, which must be 

 removed in turn by washing in distilled water. In some 

 cases access of air can be prevented by coating specimens 

 with wax or varnish. 



Friable shells are best preserved by impregnation 

 with size or shellac. The latter (in alcoholic solution) 

 is preferable, since it does not become sticky in damp 

 surroundings. A trace of corrosive sublimate added to 

 either solution inhibits the growth of mould, which may 

 otherwise cause trouble. 



The methods of mounting microscopic objects such 

 as Foraminifera or Radiolaria are similar whether the 

 specimens are recent or fossil ; no details need be given 

 here. It may, however, be noted that such small fossils 

 (when separated from their matrix) are usually best 

 studied in reflected light, and can be placed in air cells 

 rather than any special medium. 



(C) TAXONOMY 



The classification and nomenclature of fossils is 

 attended with difficulties far greater than those en- 

 countered in biological taxonomy, serious as they may 

 prove when living creatures are concerned. Increase 

 of knowledge leads inevitably towards complication of 

 classification, since all schemes involve more or less 

 arbitrary subdivision of series that are essentially con- 

 tinous. No two organisms are likely to be exact 

 duplicates, even when they belong to the same genera- 

 tion or are born of the same parents. So that in 

 palaeontological material, where a difference in horizon 

 of a few feet may mean the separation of two related 

 organisms by many series of generations, accurate 

 definition of specific characters is inconceivable. No 



