PRESUMPTIVE 

 EPIDERMIS 



YOLK 

 PLUG 



BLASTOCOEL 



Tot A trZ r arran «7 ent 0f the P^umptive regions during gastruladon. 

 therein **&** ™7 «>ly gastrula. Beg.nning at L dorsal lip, 



he regions are numbered consecutively above the lip and lettered below the 

 hp Bono,, Regrons 1 through 5, including the presumptive notochord, move 

 to take an rnternal posrtmn and form the roof of the archenteron 



