222 



VITAL STAINING AND MOR PHOGENET I C MOVEMENTS 



GASTRULATION 

 IN THE 

 FROG 



ORGAN PRIMORDIA 



PRESUMPTIVE NEURAL PLATE 



DORSAL 



LATERAL ) LIPS <f BLASTOPORE 



VENTRAL J 



LATE GASTRULA- STAGE 



(MODIFIED FROM VOGT 1929) 



