EVOLUTION IN NATURE 165 



of reasonably great degrees of evolution that we 

 must turn to these faulty records for illustrations 

 of the evolution of species. In spite of their in- 

 completeness, the materials of palaeontology afford 

 a number of significant facts concerning evolu- 

 tionary processes. In such phylogenetic series as 

 the oft-cited horses, elephants, and camels, the 

 cephalopods, and the series of greater taxonomic 

 scope and consequent poverty of detail, two facts 

 stand out with striking clarity. First, evolution 

 has taken place in connection with gradually 

 changing environments, and second, it has been 

 accomplished by gradual change of the organisms 

 involved. These facts are quite in harmony with 

 the conclusions already cited from theoretical in- 

 terpretation of conditions among existing organ- 

 isms. Together they furnish justification little 

 short of actual proof for this interpretation of 

 evolutionary processes, and a majority of biologists 

 will be found to concur in this interpretation. 



Another consideration which arises from the 

 entire field of evidence is the relationship of new 

 characters to the preexisting organic complex. We 

 speak of them commonly as if they appeared sud- 

 denly in a fully developed state, or as an absolute 

 departure from preexisting conditions, during the 

 course of phylogeny. This is only a matter of ex- 

 pression; we must deal with the origin of charac- 

 ters as we deal with the origin of species, even while 



