3i6 



Appeiidixes 



positions of the constituents of the cells may perhaps be 

 maintained throughout the history of the tissues, It is 

 easier to suppose that the original planes of embryonic 

 division are determined according to these positions than 

 that their influence can operate after complex somatic 

 differentiation has been brought about. 



At some early stage in the embryonic development or 

 perhaps In later apical divisions we can suppose that the 

 n— I cells of the parental constitution are formed by 

 successive perlcllnal and anticlinal divisions of the original 

 quadrants which occupy corresponding positions. The 

 accompanying diagram gives a schematic representation of 

 the process as we Imagine it. Obviously It does not pre- 

 tend to give more than a logical or symbolic presentation 



AB X ab 



Ab X aB 



n-1 



n- 1 



n - 



lAb 



Iba 



Sab 



3Ab 



IBa 



lAB 



Fig. 39- 



