CHAPTER XXIII 

 THE EVOLUTION OF SYMMETRY 



The subject of Symmetry is a very wide one, including 

 as it does symmetry of Form, of Power, of Time, and of 

 Numbers ; but what we are concerned with is the evolution 

 of Symmetry of Form in cellularly-continuous organisms. It 

 is symmetry of form accompanying Continuity. 



There is, it is true, a symmetry of form which may 

 accompany Discontinuity, in the sense that free and inde- 

 pendent organisms could be symmetrical with each other. 

 Thus, the measurements of one fish could, in all directions, 

 be exactly those of another. This, however, we may put 

 on one side as of no interest ; our attention being taken up 

 with the fact that the fish, an organism built up of many 

 cells in close continuity, is itself bilaterally symmetrical. 



It is quite clear that symmetry of form need not be the 

 accompaniment of Continuity, for just as a very asymmet- 

 rical house may be built up with a number of similar bricks, 

 so might the union of many cells result in an asymmetrical 

 organism. In fact, we may say that asymmetry of form 

 would be the inevitable accompaniment of Continuity 

 unless the uniting factor so worked as to produce symmetrical 

 results, or exercised symmetrical power. 



In the following brief remarks regarding the evolution 

 of living symmetry the independent protoplast, or cell, of 

 the Discontinuous Multicellular Individual has been taken 

 as the unit, or " brick," with which Nature has worked to 

 produce its balanced effects. The cell, of course, is itself 

 a wonderful organism with a living Continuity of its own, 

 and it may be of symmetrical measurements, or it may not ; 

 but it is evident that the symmetry of form of cellularly- 

 continuous organisms is in no way due to cell-symmetry. 

 The cells of living tissues show endless variation in details 

 of size and shape, and can only be described as being similar 

 to each other. They are not really comparable with " bricks." 



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