CHAPTER IX 



THE TRIAXIAL SYSTEM AND THE GREAT 

 HIGHWAY OF ANIMAL EVOLUTION 



The Triaxial System of Structural and Functional Gradients Its 

 Methods of Internal Readjustment and Betterment The Material 

 and Functional Register of Vital Betterments: the Old Mouth and 

 the New; Gills, Lungs, and Heart; the Blood; the Nervous System 

 The Decline of Metamerism and the Centralization of Func- 

 tions Architectural Tropism, or the Orientation of Triaxial Or- 

 ganic Gradients to the Triaxial System of Gradient Action in the 

 Outer World: the Asymmetry of the Outer World; the Orientation 

 of Triaxial Vital Architecture to World Architecture; Tropic Action; 

 Triaxial Architecture as a Tropic Reaction System and as a Product 

 of Tropic Action Other Registers of Constructive Action, Instincts, 

 Intelligence, Cultural Implements Cultural Registers. 



IN "The Evolution of the Vertebrates and Their 

 Kin," we have shown that man is the culminating prod- 

 uct of a long genetic line called The Great Highway 

 of Animal Evolution. It emerges from the coelenter- 

 ate stock, probably as a special modification of the 

 radial mode of growth, and in successive adaptive in- 

 crements leads by way of the more primitive arthro- 

 pods, such as the phyllopod Crustacea and marine 

 arachnids, up to the ostracoderms (a wholly extinct 

 class of animals forming a paleozoic connecting link 

 between the invertebrates and the vertebrates) through 

 them to the fishes, amphibia, reptiles, and mammals, to 

 man, where it culminates in its logical constructive lim- 

 itation, figs. 7 and 8. 



Throughout this great phylogenetic line, there is a 

 common architectural plan and a consistent method 



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