DYNAMICS OF MORPHOGENESIS 



135 



Fig. 46 Diagram, indicating levels of section. The two chief regions of fission 

 are indicated bj" stippling at xa; and \jy: the length of stippled region indicates 

 approximately the range of variation of the level of fission in different animals of 

 the same size from the same stock and the density of shading indicates the fre- 

 quency at different levels. 



