VITAL STAINING AND MORPHOGENETIC MOVEMENTS 



207 



GASTRULATION 

 IN THE 

 FROG 



ORGAN PRIMORCHA 



v»)*^ 



PRESUfPTIVE NEURAL PLATE 



LATERAL > LIPS ^ BLASTOPORE 



'^r 



VENTRAL J 



LATE GASTRULA-STAGE 



( MODIFIED FROM VOGT 1929 ) 



Paths of displacement in 

 gastrulation. Based on Vogt. 



(From Ward's Natural Science 

 Establishment Inc. Dr. J. 

 Mueller) 



