CLASSIFICATION 287 



If there were a complete genealogical record it would be pos- 

 sible to make the various grades of classification correspond 

 to degrees of relationship ; but, as the record cannot be com- 

 plete, such a correspondence is impossible, and we can only 

 deal according to the best of our judgment with the evidence 

 at our disposal. A classification, then, can only be regarded 

 as an approximate representation of animal affinities ; but, such 

 as it is, it should represent the fullest extent of our knowledge. 

 Classifications must change as knowledge advances. 



