HIGHWAY OF ANIMAL EVOLUTION 241 



bratory action, or chemical emissions, such as sound, 

 odors, color, etc. All these influences, in the main, are 

 propagated in this horizontal plane, in north and south, 

 east and west, or intermediate directions, at gradient 

 rates and with gradient momentum. 



2. The Orientation of Triaxial Vital Architecture 

 to World Architecture. The definite orientation of the 

 triaxial system to this world action system is seen in the 

 stable relation of the neuro-haemal axis to the two most 

 constant directive agencies of the outer world, that is, to 

 gravity, the more constant and dominant one, and in a 

 lesser degree, to light, the less constant one. 



While in the arthropods the normal, or functional, 

 position of the body during locomotion is such that the 

 neural side may be directed either upwards or down- 

 wards (depending largely on whether the animal is 

 in a walking, or swimming, position) in the verte- 

 brates, it is almost without exception directed up- 

 wards, or away from the earth's centre of gravity. In 

 either case, the whole body is architecturally and func- 

 tionally balanced, other things being equal, only when 

 the neuro-haemal axis is parallel with the lines of 

 gravity. This force is universal ; it casts no shadows, 

 and all bodily actions are subject to its unvarying in- 

 fluence. Hence this architectural and functional ori- 

 entation should be, and is, the most universal and stable 

 of all morphological and physiological phenomena. 



Light has less pronounced architectural influence 

 on the body than gravity; for while light, in the main, 

 comes on rectilinear paths from above, it is subject to 

 many local and periodic variations, due to terrestrial 

 motion, incidental reflection and refraction, and com- 

 plete absorption. It is in the extraordinary variation 



