REJUVENESCENCE IN EMBRYO AND LARVA 423 



Apparently in all these cases metamorphosis is a partial physio- 

 logical disintegration of the individual resulting from changes in 

 the axial gradient during the earlier stages of development, or from 

 the aging and death of certain larval organs. Where the larval 



Fig. 198. — Larval metamorphosis of Branchipus (fairy shrimp) 



period occurs at a very early stage of development a well-marked 

 axial gradient and a relatively high degree of individuation are 

 present at the beginning, or at a very early stage, of embryonic 

 development. 



