BIOLOGICAL PALAEONTOLOGY 93 



an individual may be measured by the relative harmony 

 with which its component structures collaborate. Hence 

 a high stage of elaboration in one particular character 

 may often prove inconvenient or fatal to an organism, if 

 it fails to conform to the functional requirements of less 

 progressive features. The name "individual " thus proves 

 misleading when applied to an organism, since, although 

 the presence of all its structures may be necessary for 

 life (an infrequent and dangerous condition), each one of 

 its organs can have some independence of development 

 during " individual " growth and evolutional history. 

 From the standpoint of evolution, it is essential to 

 regard an "individual" as divisible into its several 

 structures. 



The organism is the unit of the group, and the organ 

 the unit of the "individual"; the relation of the two 

 units to their respective compounds is in some measure 

 dissimilar. Thus it follows that study of race-history 

 and that of structural evolution must be in some degree 

 independent. Hence the two words in the title of this 

 section. Phylogeny is racial evolution, morphogeny that 

 of structure. The two studies are as inseparable, and 

 as distinct, as organisms and their component organs- 

 Race-history can be traced only through the sequence 

 of individuals; progress or reversion in the latter is indi- 

 cated by the qualities of their morphological characters. 

 It follows that morphogeny must supply the basis on 

 which phylogeny can be reared. Similar relations 

 exist between Morphology and Taxonomy. System- 

 atic classification must be founded on morphological 

 discovery; phylogenetic series cannot be traced until 

 morphogenetic trends have been recognized. But it is 

 inexpedient, in either case, to await completion of the 

 foundations before erecting the superstructure. Pro- 

 visional classification, subject to continual revision, is 



