LECTURE XXXVI. 



APPLICATION OF THEORY OF DESCENT TO TAXONOMY. 

 OBJECT AND METHODS OF TAXONOMIC WORK. 



Prof. John H. Comstock. 



Object and methods before the acceptance of the 

 theory of Evolution. Making of catalogues. Group- 

 ing of related forms without understanding the bond 

 of union. 



The tracing of the phylogeny of groups. 



Aid derived from paleontology. 



Aid derived from the study of those existing forms 

 that are generalized in structure. 



Peculiar specializations of generalized forms, " side- 

 wise developments." 



Proposed method of taxonomic work. (1) The de- 

 termination of the probable form of the progenitor of 

 the group to be classified. (2) The tracing of the 

 various ways in which this form has been modified by 

 descent ; i. e., the determination of the phylogeny of 

 the group. 



Difficulties of carrying out this plan. Poorness of 

 the palseontological record. Hence, usually, the neces- 

 sity of determining the primitive type by a study of 

 existing generalized forms ; and of determining the 

 various ways in which this type has been modified by 

 a study of the more specialized of the existing mem- 

 bers of the group. 



How shall one determine which are the more gen- 



