238 GEOLOGICAL BIOLOGY. 



entirely the classifications which were made by the earliest 

 naturalists who believed in the original creation of all species. 



The difference between the two methods is quite simple, 

 and may be explained in a few words. Cuvier and his school 

 observed the morphological characters of organisms, not al- 

 ways knowing the exact physiological function, and compared 

 them together, and then wrote descriptions of the differences 

 they observed. They separated organisms into distinct spe- 

 cies and genera by the different characters they observed in 

 each, and thus their method of classification is based upon 

 observed differences in form. The new school of naturalists 

 is intent, first of all, upon the discovery of the affinities of 

 each kind of organism studied. Their point of view is di- 

 rectly the reverse of their predecessors. Their descriptions, 

 and finally their classifications, are based upon the points of 

 resemblance which can be detected upon comparing different 

 organisms with each other. 



Analytic and Synthetic Method of Classification. These two 

 schools differ as to the kind of characters which they consider 

 to be of chief importance in classification, and, as a general 

 effect upon classification, the one school is apt to overesti- 

 mate imagined resemblances, not to be seen by the ordinary 

 observer, and the other may err on the side of making too 

 much of external, often trivial, characters. 



Irrespective of the way by which the two methods of clas- 

 sification arose, both methods are now in use and both are 

 useful. 



In order to give them names, free from any accidental as- 

 sociation connected with their origin or application, the first 

 may be called the analytic method of classification, the second 

 may be called the synthetic method; and for the purposes of 

 illustration Zittel's classification of the Molluscoidea and Mol- 

 lusca may be selected as examples of the analytic method, 

 and Lankester's classification of the Mollusca may be taken 

 as an example of a synthetic classification. 



Here, as elsewhere in this treatise, the reader must be left to learn the 

 full meaning of the descriptions, only outlined, by a study of the objects 

 themselves. No possible description of natural objects, particularly or- 

 ganisms, can convey to a student impressions which he has never before 

 experienced. And the best way for any one to gain a true notion of the 



