78 



STAGING OF AMPHIBIAN EMBRYOS 



37 



21. Exo-gastrula in which 2/5 of yolk is unincorporated. 



22. Gostnilation achieved although dorsal lip lias been damaged. 



23. Exo-gastrula in which 2/S of yolk is unincorporated. 



24. Hemi-gastrula. 



25. - 26. Embryonic areas attempting to develop without incorporated yolk. 

 27. - 39. Various degrees of exo-gostrulation. 



40. Fairly normal yolk plug but irregular dorsal lip which will condition ahnormalities in the embryo. 



RANA PIPIENS 



