C— GEOLOGY 75 



of others that may be of vital importance. No organism can thrive 

 unless its components work in harmony ; no harmony can be held for long 

 when the several structures follow their own rates and directions of 

 modulation. Doubtless this self-evident condition affects every com- 

 ponent of every organism ; to the palaeontologist the note that seems 

 doomed to modulate into discord is that of mineral secretion. 



It must be obvious to all that the course of morphogeny just sketched 

 is closely analogous with the history of individual life ; or, for that matter, 

 of political and economic affairs. The whole issue boils down to the 

 simple proposition that structures, organisms or states arise, gradually 

 reach maturity, and then pass beyond it to destruction. An important 

 aspect of the matter, however (again platitudinous, but often overlooked), 

 is that the smaller and unconsidered ingredients may often be the final 

 arbiters. It avails nothing for an organism or a body politic to be in 

 otherwise perfect order if one of its ingredients is out of proportion. 

 An organism or a kingdom, if divided against itself, cannot stand. 



There is thus a twofold Nemesis awaiting all living creatures. Environ- 

 mental change may outpace their powers of adaptation, and so destroy 

 them ; or, if this external disaster is avoided, the means adopted to elude 

 it proceed relentlessly towards a disproportion that means failure. The 

 gloomy conclusion we have now reached implies nothing more unexpected, 

 or more encouraging, than that for races, as for individuals, there exist 

 but two alternatives, natural or accidental death. 



We are now in a position to summarise the palaeontological evidence 

 as to the manner of evolution. Palaeontology gives no direct evidence 

 as to the origin of groups, of whatever taxonomic grade ; its scope is 

 limited to records of the later stages in the careers of groups already 

 in existence. This is not to deny that the presumptive evidence for the 

 birth of new types is overwhelmingly strong ; but actual tangible proof 

 of their parentage and generation is lacking. A palaeontologist is more 

 of an undertaker than a midwife. 



Again, fossil evidence cannot give convincing demonstration of the 

 origin of structures in organisms ; its scope is restricted to observation 

 of the fate of those structures after they have appeared. There must 

 always be a theoretical quality in attempted explanations of the develop- 

 ment of new characters ; there are facts recording what happens to them 

 in course of time. 



The only language which adequately expresses the nature of morpho- 

 geny is that used in description of individual life. Structures, once 

 originated, pass through stages of development, modification and ampli- 

 fication that are closely analogous to the phases of personal history, both 

 physical and psychological. There is a continuous duplicity, in that 

 intrinsic characters are involved with external requirements ; environment 

 is educative but not creative. There is a limit to the response to environ- 

 ment possible for any structure ; if that limit is exceeded, disaster results. 

 Every character of an organism, like every complete creature, is more 

 responsive to environmental influence in its early history than later. 

 Directions of development induced or encouraged by environment 



