STAGING OF AMPHIBIAN EMBRYOS 



63 



¥ < 



GILLS 



OPERCULAR FOLD 



RK3HT SIDE 



GILLS 



LEFT SIDE 



OPERCULAR FOLD AND TEETH - STAGE 23 



VENTRAL VEW 



MOt/TH 



EVE 



VENTRAL VIEW 



OPEN OPERCULUM 



(STAGES 23 a 25 REDUCED 33 * 

 AS COMRUED WITH SERES) 



OPERCULUM COMPLETE - STAGE 25 



(RANA PIPtENS) 



