98 GEOLOGICAL BIOLOGY. 



the resultant of these two forces, ancestry and environment, 

 working together. 



The soft, active organs are the chief parts of study for the 

 zoologist; they best express the stages of ontogenetic devel- 

 opment, but the characters of the hard parts best record the 

 phylogenetic evolution. So long as there is plasticity in the 

 characters themselves there is possible adjustment, but when 

 we find a rigid resisting body formed, it expresses a perma- 

 nent step taken in the evolution and established. 



Fossils and Geological Biology. Geological biology treats of 

 the organism as a unit, with its relations to its ancestors, to 

 its race, to time, and to environment ; zoological biology 

 treats each organism as a complex bundle of organs with 

 their numerous functions adjusted together, but ever distin- 

 guished by their specific histological and anatomical peculiari- 

 ties. The zoologist studies organs and functions as they are 

 combined in the individual organism ; the paleontologist 

 studies varieties and species as they are combined to make up 

 faunas and races, and as adjusted to the varying conditions of 

 time and place. In studying a fossil he asks, not only and 

 not chiefly, what place has it in systematic classification ? but 

 how is it related to what has gone before, and what is its 

 ancestry? and how is the organism related to what follows, 

 or of what is it prophetic? 



These questions lead us to seek such characters as will 

 indicate, first, genetic affinities and, second, effects of environ- 

 ment. 



Hard Parts express both Relation to Environment and Relation 

 to Ancestry. For these purposes the hard parts are of the 

 greatest value, and why? The hard parts are such as teeth; 

 organs of offence and defence, as horns, hoofs, spines, scales, 

 shells ; and skeletons, external and internal. They represent, 

 not the active vital part of the animal, but some part built 

 up between the living animal and nature ; hence they have 

 an outer and an inner surface, the outer suffers degradation 

 with use ; the inner expresses the form assumed by the ani- 

 mal in the natural function of animal growth. Fossils are 

 the result of growth, and hence express the final morpho- 

 logical result of the living individual. As hard parts they 



